Phosphor and production method thereof, phosphor-containing composition, light emitting device, illuminating device, display, and nitrogen-containing compound

ABSTRACT

To provide a new phosphor of which fluorescence contains much red light component and has a large full width at half maximum, the crystal phase represented by the formula [I] is included in the phosphor.
 
R 3−x−y−z+w2 M z A 1.5x+y−w2 Si 6−w1−w2 Al W1+w2 O y+w1 N 11−y−w1   [I]
 
(R represents La, Gd, Lu, Y and/or Sc, M represents Ce, Eu, Mn, Yb, Pr and/or Tb, A represents Ba, Sr, Ca, Mg and/or Zn, and x, y, z, w1 and w2 are the numeric values in the following ranges:
 
( 1/7)≦(3 −x−y−z+w 2)/6&lt;(½),
 
0&lt;(1.5 x+y−w 2)/6&lt;(9/2),
 
0&lt;x&lt;3,
 
0≦y&lt;2,
 
0&lt;z&lt;1,
 
0≦w1≦5,
 
0≦w2≦5, and
 
0 ≦w 1 +w 2≦5)

TECHNICAL FIELD

The present invention relates to a phosphor comprising anitrogen-containing compound such as complex nitride or oxynitride and aproduction method thereof, to a phosphor-containing composition, and toa light emitting device, a display and an illuminating device using thesame. More particularly, it relates to a phosphor that emits yellowgreen to orange light when irradiated with light from an excitationlight source such as a semiconductor luminous element, which serves as afirst luminous body, to a phosphor-containing composition comprising thesame, to a high-efficiency light emitting device, a display, and anilluminating device using the same, and to a nitrogen-containingcompound.

BACKGROUND ART

Though nitrides are inferior to oxides in facilitation of production,not a few of them are known to have characteristics which oxides orother inorganic compounds do not have. Actually, such binary systemnitrides as Si₃N₄, BN, AlN, GaN and TiN are used for various purposessuch as substrate material, semiconductor, light emitting diode(hereinafter abbreviated as “LED” as appropriate), structural ceramicsand coating agent, and in industrial-scale production.

In addition, large numbers of new substances of ternary or highernitrides are in production in these years. Among them, phosphormaterials with superior characteristics made of particularly oxynitridesor multinary nitrides based on silicon nitride have been developedrecently. It is known that these phosphor materials emit yellow to redlight when excited by a blue LED or a near-ultraviolet LED.

Such combinations of those phosphors and a blue or near-ultraviolet LEDcan constitute a light emitting device emitting white light.

For example, Patent Document 1 discloses a white light emitting devicein which a blue LED or LD chip of nitride-based semiconductor iscombined with a cerium-activated yttrium aluminium garnet phosphor ofwhich Y is partly substituted with Lu, Sc, Gd, or La. The white lightemitting device can produce a white light by combining a blue light,generated from the LED, and a yellow light, generated from the phosphor.The white light emitting device is already in practical use for displayor the like.

A phosphor comprising a Ce-activated nitride or oxynitride with aJEM-phase silicon oxynitride as the host material is known (Non-PatentDocument 1).

In addition, as another phosphor having a nitride as the host mateiral,La₃Si₆N₁₁:Ce is known (Patent Document 2).

Moreover, as known nitrides containing an alkaline-earth metal element,a trivalent rare-earth element and silicon, SrYbSi₄N₇ and BaYbSi₄N₇ areknown to have a space group of P6₃mc (Non-Patent Document 2), andBaEu(Ba_(0.5)E_(0.5))YbSi₆N₁₁ is known to have a space group of P2₁3(Non-Patent Document 3).

[Patent Document 1] Japanese Patent Laid-Open Publication No. Hei10-190066

[Patent Document 2] Japanese Patent Laid-Open Publication No.2003-206481

[Non-Patent Document 1] Preprints of Meeting, 316th, Phosphor ResearchSociety, pp. 23

[Non-Patent Document 2] Zeitschrift fur Anorganische und AllgemeineChemie, 1997, vol. 623, pp. 212

[Non-Patent Document 3] H. Huppertz, a thesis for a doctorate, BayreuthUniv., 1997

DISCLOSURE OF THE INVENTION Problem to Be Solved by the Invention

However, the white light emitting device disclosed in Patent Document 1has a problem of low color rendering of the light emitted, for the useof an illuminating device. Namely, the aforementioned cerium-activatedyttrium aluminium garnet phosphors have little red light component inthe emission spectrum. Accordingly, it has been difficult to realize aillumination light with low color temperature and high color rendering,like “warm white” (JIS Z8110) of fluorescent lamps, which is a colorfelling warm, by combination of a cerium-activated yttrium aluminiumgarnet phosphor and a blue LED. Therefore, a phosphor that shows morered light component than cerium-activated yttrium aluminium garnetphosphors and of which emission spectrum has a large full width at halfmaximum has been desired.

However, the luminescent color of the phosphor described in Non-PatentDocument 1 ranges from blue to green. The phosphor described in PatentDocument 2 emits a blue light. Regarding Non-Patent Documents 2 and 3,there are no descriptions about features of their phosphors. In theresult, the above-mentioned problem can not be solved by previouslyknown phosphors such as those described in Patent Documents 1 and 2,Non-Patent Documents 1 to 3, and the like.

The present invention has been made to solve the above problems. Theobject thereof is to provide a new phosphor with large full width athalf maximum and a production method thereof, a phosphor-containingcomposition, a light emitting device, a display and an illuminatingdevice using the phosphor, and also a nitrogen-containing compound usedfor the phosphor.

Means for Solving the Problem

The inventors of the present invention have made an intensiveinvestigation to solve the above problems. In consequence, they havefound a totally new nitrogen-containing compound, such as nitride,oxynitrides or the like, and they have found that a phosphor having acrystal phase of that nitrogen-containing compound can exhibit aremarkably excellent characteristics as a high-performance yellow greento orange phosphor and is preferably used for a light emitting device orthe like. In addition, they also investigated the production methodthereof, which led to the completion of the present invention.

Namely, the phosphor of the present invention (I) is a phosphorincluding a crystal phase represented by the formula [I] (claim 1).R_(3−x−y−z+w2)M_(z)A_(1.5x+y−w2)Si_(6−w1−w2)Al_(W1+w2)O_(y+w1)N_(11−y−w1)  [I](In the formula [I],

-   R represents at least one kind of a rare-earth element selected from    the group consisting of La, Gd, Lu, Y and Sc,-   M represents at least one kind of a metal element selected from the    group consisting of Ce, Eu, Mn, Yb, Pr and Tb,-   A represents at least one kind of a bivalent metal element selected    from the group consisting of Ba, Sr, Ca, Mg and Zn, and-   x, y, z, w1 and w2 are the numeric values in the following ranges:    ( 1/7)≦(3−x−y−z+w2)/6<(½),    0<(1.5x+y−w2)/6<(9/2),    0<x<3,    0≦y<2,    0<z<1,    0≦w1≦5,    0≦w2≦5, and    0≦w1+w2≦5)

In this case, it is preferable for the phosphor of the present invention(I) that the wavelength of emission peak when excited with light of460-nm wavelength is 480 nm or longer (claim 2).

Further, it is preferable for the phosphor of the present invention (I)that the color coordinates x and y, in CIE standard colorimetric system,of the luminescent color when excited with light having 460-nmwavelength are in the ranges of 0.420≦x≦0.600 and 0.400≦y≦0.570,respectively (claim 3).

The phosphor of the present invention (II) is a phosphor including acrystal phase represented by the formula [II] below and produced using,as at least a part of the raw material, an alloy containing two or morekinds of the metal elements that are included in said crystal phase(claim 4).R_(3−x−y−z+w2)M_(z)A_(1.5x+y−w2)Si_(6−w1−w2)Al_(W1+w2)O_(y+w1)N_(11−y−w1)  [II](In the formula [II],

-   R represents at least one kind of a rare-earth element selected from    the group consisting of La, Gd, Lu, Y and Sc,-   M represents at least one kind of a metal element selected from the    group consisting of Ce, Eu, Mn, Yb, Pr and Tb,-   A represents at least one kind of a bivalent metal element selected    from the group consisting of Ba, Sr, Ca, Mg and Zn, and-   x, y, z, w1 and w2 are the numeric values in the following ranges:    ( 1/7)≦(3−x−y−z+w2)/6<(½),    0≦(1.5x+y−w2)/6<(9/2),    0≦x<3,    0≦y<2,    0<z−1,    0≦w1≦5,    0≦w2≦5, and    0≦w1+w2≦5)

In this case, it is preferable for the phosphor of the present invention(II) that the wavelength of emission peak when excited with light of460-nm wavelength is 480 nm or longer (claim 5).

Further, it is preferable for the phosphor of the present invention (II)that the emission spectrum when excited with light of 460-nm wavelengthsatisfies the formula [B] below (claim 6).I(B)/I(A)≦0.88  [B](In the above formula [B],

-   I(A) represents the emission intensity of the maximum peak    wavelength that is present in the wavelength range of 500 nm or    longer and 550 nm or shorter, and-   I(B) represents the emission intensity of the wavelength that is    longer than the maximum peak wavelength by 45 nm.)

Further, it is preferable for the phosphor of the present invention (II)that in the powder X-ray diffraction pattern measured with CuKα line(1.54184 Å), a peak exists at 2θ from 17° to 20°, and the peak intensityratio I, related to a peak present at 2θ from 21° to 24°, is 0.05 orsmaller (claim 7).

The above-mentioned peak intensity ratio I is, in the powder X-raydiffraction pattern at 2θ ranging from 10° to 60°, the ratio of heightI_(p) of the peak, present at 2θ from 21° to 24°, to height I_(max) ofthe most-intensive peak, present at 2θ from 17° to 20°, and the valuesof the peak intensities are used after background correction.

Further, it is preferable for the phosphor of the present invention (II)that in the above-mentioned formula [II], x and y satisfy0<(1.5x+y−w2)/6<(9/2) and 0<x<3 (claim 8).

Further, it is preferable for the phosphor of the present invention (II)that the color coordinates x and y, in CIE standard colorimetric system,of the luminescent color when excited with light having 460-nmwavelength are in the ranges of 0.320≦x≦0.600 and 0.400≦y≦0.570 (claim9).

Further, it is preferable for the phosphor of the present invention (II)that the full width at half maximum of the emission peak when excitedwith light of 460-nm wavelength is 100 nm or longer (claim 10).

The production method of the present invention is a production method ofa phosphor including a crystal phase represented by the above-mentionedformula [II], using, as at least a part of the raw material, an alloycontaining two or more kinds of the metal elements that are included insaid crystal phase, and comprising a step of nitriding in which thealloy is fired in a nitrogen-containing atmosphere (claim 11).

In this case, it is preferable that the alloy and a nitride are used asthe raw material (claim 12).

The phosphor-containing composition of the present invention comprisesthe above-mentioned phosphor (I) and/or phosphor (II) and a liquidmedium (claim 13).

The light emitting device of the present invention comprises: a firstluminous body and a second luminous body that emits visible light whenirradiated with light from said first luminous body, wherein said lightemitting device comprises, as said second luminous body, a firstphosphor including at least one kind of the above-mentioned phosphor (I)and/or phosphor (II) (claim 14).

In this case, it is preferable that the light emitting device of thepresent invention comprises, as said second luminous body, a secondphosphor including at least one kind of a phosphor of which wavelengthof emission peak is different from that of said first phosphor (claim15).

The illuminating device of the present invention comprises a lightemitting device of the present invention (claim 16).

The display of the present invention comprises a light emitting deviceof the present invention (claim 17).

The nitrogen-containing compound of the present invention includes acrystal phase represented by the above-mentioned formula [I] (claim 18).

Advantageous Effect of the Invention

According to the present invention, a new phosphor that can emit afluorescence containing a large amount of red component and having alarge full width at half maximum, a phosphor-containing composition, alight emitting device, an illuminating device and a display using thephosphor, and also a nitrogen-containing compound used for the phosphorcan be achieved.

In addition, the phosphor produced by the production method of thepresent invention is excellent in its luminescent characteristics suchas emission intensity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view illustrating the positionalrelationship between the first luminous body, which functions as theexcitation light source, and the second luminous body, a componentfunctioning as the phosphor-containing part that contains a phosphor, inan example of the light emitting device of the present invention.

FIG. 2( a) and FIG. 2( b) are schematic sectional views illustratingexamples of the light emitting device having an excitation light source(first luminous body) and a phosphor-containing part (second luminousbody). FIG. 2( a) shows a typical example of the light emitting devicegenerally called a shell type. FIG. 2( b) shows a typical example of thelight emitting device generally called a surface-mount type.

FIG. 3 is a schematic view of an example of a surface-emittingilluminating device incorporating the light emitting device.

FIG. 4 is a graph showing emission spectral maps of the phosphor ofExample I-8, the commercially available Y₃Al₅O₁₂:Ce phosphor, and theLaSi₃N₅:Ce phosphor of Comparative Example I-1, of the presentinvention.

FIG. 5 is a graph showing the powder X-ray diffraction pattern of thephosphor, which was washed with aqua regia, of Example I-8 of thepresent invention.

FIG. 6 is a graph showing the emission spectral maps of the phosphorsprepared in Examples I-17 to I-24 of the present invention.

Both FIG. 7( a) and FIG. 7( b) are graphs showing the characteristics ofthe phosphor prepared in Example I-18 of the present invention. FIG. 7(a) shows the excitation spectrum. FIG. 7( b) shows the emissionspectrum.

FIGS. 8( a), 8(b), and 8(c) are graphs showing the powder X-raydiffraction patterns of the phosphors prepared in Examples I-17, I-22,I-36 of the present invention, respectively.

FIG. 9 is a graph showing the emission spectral maps of the phosphorsprepared in Examples I-8, I-26 to I-28 of the present invention.

FIG. 10 is a graph showing the emission spectral maps of the phosphorsprepared in Examples I-30 to I-32 of the present invention.

FIG. 11 is a graph showing the emission spectral map of the lightemitting device prepared in Example I-39 of the present invention.

FIG. 12 is a graph showing the emission spectral maps of the phosphorsprepared in Examples II-1, II-2 and II-3 of the present invention.

FIG. 13 is a graph showing the powder X-ray diffraction patterns of thephosphors prepared in Examples II-3, II-4, and Reference Example II-1 ofthe present invention, respectively.

FIG. 14 is a graph showing the emission spectral maps of the phosphorsprepared in Examples II-4 to II-8 and Reference Example II-1 of thepresent invention.

FIG. 15 is a graph showing the emission spectral map of the lightemitting device prepared in Example II-14 of the present invention.

EXPLANATION OF LETTERS OR NUMERALS

1 phosphor-containing part (second luminous body) 2 surface-emittingtype GaN-based LD (excitation light source, first luminous body) 3substrate 4 light emitting device 5 mount lead 6 inner lead 7 excitationlight source (first luminous body) 8 phosphor-containing resinous part 9conductive wire 10 mold member 11 surface-emitting illuminating device12 holding case 13 light emitting device 14 diffusion plate 22excitation light source (first luminous body) 23 phosphor-containingresinous part (phosphor- containing part, second luminous body) 24 frame25 conductive wire 26 electrode 27 electrode

BEST MODES FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be explained in detailbelow. It is to be understood that the present invention is not limitedto the following embodiment and any modification can be added theretoinsofar as they do not depart from the scope of the present invention.

All the relationships between color names and their color coordinates inthe present Description comply with the Japanese Industrial Standards(JIS Z8110 and Z8701).

Each composition formula of the phosphors in this Description ispunctuated by a comma (,). Further, when two or more elements arejuxtaposed with a comma (,) in between, one kind of or two or more kindsof the juxtaposed elements can be contained in the composition formulain any combination and in any composition. For example, a compositionformula, “(Ca,Sr,Ba)Al₂O₄:Eu”, inclusively indicates all of“CaAl₂O₄:Eu”, “SrAl₂O₄:Eu”, “BaAl₂O₄:Eu”, “Ca_(1−x)Sr_(x)Al₂O₄:Eu”,“Sr_(1−x)Ba_(x)Al₂O₄:Eu”, “Ca_(1−x)Ba_(x)Al₂O₄:Eu” and“Ca_(1−x−y)Sr_(x)Ba_(y)Al₂O₄:Eu” (here, in these formulae, 0<x<1, 0<y<1,0<x+y<1).

[1. Phosphor (I)]

[1-1. Crystal Phase of Phosphor (I)]

The present inventors made a search for nitrides and oxynitrides ofrare-earth elements, alkaline-earth metals and Si, for obtaining a newphosphor. As a consequence, they have found a substance including acrystal phase with a composition range represented by the generalformula [I] below.

Namely, the phosphor of the present invention (I) includes a crystalphase represented by the general formula [I] below.R_(3−x−y−z+w2)M_(z)A_(1.5x+y−w2)Si_(6−w1−w2)Al_(W1+w2)O_(y+w1)N_(11−y−w1)  [I](In the general formula [I], R represents at least one kind of arare-earth element selected from the group consisting of La, Gd, Lu, Yand Sc. M represents at least one kind of a metal element selected fromthe group consisting of Ce, Eu, Mn, Yb, Pr and Tb. A represents at leastone kind of a bivalent metal element selected from the group consistingof Ba, Sr, Ca, Mg and Zn. And, x, y, z, w1 and w2 are the numeric valuesin the following ranges:( 1/7)≦(3−x−y−z+w2)/6<(½),0<(1.5x+y−w2)/6<(9/2),0<x<3,0≦y<2,0<z<1,0≦w1≦5,0≦w2≦5, and0≦w1+w2≦5.)

In the following, explanation will be given on the crystal phaserepresented by the general formula [I] in more detail.

Regarding R:

In the general formula [I], R represents at least one kind of arare-earth element selected from the group consisting of La, Gd, Lu, Yand Sc. Among them, R is preferably at least one kind of a rare-earthelement selected from the group consisting of La, Lu and Y.Particularly, it is preferably La.

As R, either a single kind of rare-earth element can be used, or acombination of two or more kinds of them can be used in any combinationand in any ratio. By using two or more kinds of rare-earth elements asR, the excitation wavelength and luminous wavelength of the phosphor ofthe present invention (I) can be adjusted.

However, when the R consists of two or more kinds of elements, it ispreferable that the R includes at least one kind of a rare-earth element(this will be referred to as “the first element”) selected from thegroup consisting of La, Lu and Y and the ratio of the first element usedrelative to the total amount of R is usually 70 mole percent or larger,preferably 80 mole percent or larger, and particularly preferably 95mole percent or larger. In this case, the ratio of the elements otherthan the first element (this will be referred to as “the secondelement”) of the above-mentioned R is therefore usually 30 mole percentor smaller, preferably 20 mole percent or smaller, and particularlypreferably 5 mole percent or smaller. This makes it possible to improvethe emission intensity.

Regarding M:

In the general formula [I], M represents at least one kind of a metalelement selected from the group consisting of Ce, Eu, Mn, Yb, Pr and Tb.In this context, M serves as an activation element. As the M, either onekind of the above-mentioned metal elements can be used, or two or morekinds of them can be used in any combination and in any ratio.

Among them, it is preferable that the M includes at least Ce from thestandpoint of good emission efficiency and wavelength of emission peak.It is more preferable that only Ce is used as M.

In the phosphor of the present invention (I), at least a part of Ce, anactivation element, is present in a state of trivalent cation. Ce, theactivation element, can be of trivalent or tetravalent valence. However,in this case, it is preferable that the content of trivalent cations ishigher. Specifically, the content ratio of Ce³⁺ to the whole amount ofCe is usually 20 mole percent or more, preferably 50 mole percent ormore, more preferably 80 mole percent, and particularly preferably 90mole percent or more.

In the same way as Ce, cations of different valences of the respectiveactivation elements other than Ce, namely, Eu, Mn, Yb, Pr and Tb, mayalso coexist. In such a case, for each element, it is preferable thatthe content of Eu²⁺, Mn²⁺, Yb²⁺, Pr³⁺ and Tb²⁺ is higher. For Eu²⁺, Mn²⁺and Pr³⁺, the preferable content is the same as that described above forCe³⁺ specifically. For Yb²⁺ and Tb²⁺, the content of bivalent cations tothe whole amount of respective elements is usually 10 mole percent ormore, preferably 20 mole percent or more, more preferably 40 molepercent, and still more preferably 60 mole percent or more,specifically.

The content of Ce³⁺ to the whole amount of Ce contained in the phosphorof the present invention (I) can be examined by a measurement for itsX-ray absorption fine structure, for example. Namely, the content can bedecided quantitatively from the areas of each-separated absorption peaksof Ce³⁺ and Ce⁴⁺, which can be obtained by a measurement for theL3-absorption edge of Ce atom. The content of Ce³⁺ to the whole amountof Ce contained in the phosphor of the present invention (I) can bedecided also by a measurement of electron spin resonance (ESR). For theabove-mentioned M, the ratio of atoms having desired valence can bedecided in the same way as Ce by a measurement of its X-ray absorptionfine structure.

Regarding A:

In the general formula [I], A represents at least one kind of a bivalentmetal element selected from the group consisting of Ba, Sr, Ca, Mg andZn. Among them, A is preferably at least one kind of a bivalent metalelement selected from the group consisting of Sr, Ca and Mg. It is morepreferably selected from Ca and Mg. It is still more preferably Ca. Asthe above-mentioned A, either one kind of these elements can be used ortwo or more kinds of them can be used in any combination and in anyratio.

The fundamental system of the crystal phase represented by theabove-mentioned general formula [I] is such that R and A coexists in asurrounding SiN₄ tetrahedron. In the crystal phase represented by theabove-mentioned general formula [I], bivalent A can be increased bydecreasing trivalent R (this substitution will be hereinafter referredto as “R-A substitution”). However, the amount of increase in A does notcorrespond just to the amount of decrease in R, but to 1.5 times of theamount thereof, causing charge compensation, which is a unique featureof the present crystal phase.

In addition, in the phosphor of the present invention (I), a part of Rmay be substituted with A in a manner other than the above-mentioned R-Asubstitution. In that case, N-anions are substituted with O-anions bythe number of R substituted.

Regarding Si and Al:

Moreover, in the above-mentioned fundamental system of the crystalphase, a part of Si may be substituted with Al. This is why Al isappeared in the general formula [I]. In that case, N-anions aresubstituted with O-anions, and/or bivalent A is substituted withtrivalent R.

Regarding Range of x:

In the general formula [I], 1.5x is a numerical value representing theamount of A substituted for a part of R by the above-mentioned R-Asubstitution. The numerical value of x in this case is larger than 0,preferably 0.002 or larger, more preferably 0.01 or larger, still morepreferably 0.03 or larger, and smaller than 3, preferably 2.7 orsmaller, more preferably 2.5 or smaller, still more preferably 2.2 orsmaller. This is because a concentration quenching may occur, when thecontent of the activation element is too large.

Regarding Range of y:

In the general formula [I], y is a numerical value representing theamount of A substituted for a part of R in the way other than theabove-mentioned R-A substitution. The smaller the numerical value of yis, the more preferable. Specifically, it is usually 0 or larger,preferably 0.01 or larger, and usually 2 or smaller, preferably 1.9 orsmaller, more preferably 1.5 or smaller, still more preferably 0.6 orsmaller.

Regarding Range of z:

In the general formula [I], z is a numerical value representing theamount of the activation element M. It is larger than 0, preferably0.002 or larger, more preferably 0.005 or larger, and smaller than 1,preferably 0.5 or smaller, more preferably 0.4 or smaller. When thevalue z is too large, the emission intensity may be lowered due to aconcentration quenching.

Regarding Ranges of w1 and w2:

In the general formula [I], the number of moles of Al substituted isrepresented by w1 and w2. The range of w1 is usually 0 or larger,preferably 0.1 or larger, more preferably 0.2 or larger, and usually 5or smaller, preferably 2 or smaller, more preferably 1 or smaller, stillmore preferably 0.5 or smaller. The range of w2 is also usually 0 orlarger, preferably 0.1 or larger, more preferably 0.2 or larger, andusually 5 or smaller, preferably 2 or smaller, more preferably 1 orsmaller, still more preferably 0.5 or smaller. Substitution with Al canadjust the color tone of the luminescent color of the phosphor of thepresent invention (I). In addition, w1 and w2 within the above-mentionedranges respectively can adjust the luminescent color with the crystalstructure remaining the same.

Regarding Conditions to be Satisfied by x, y and z:

In addition, in the general formula [I], the above-mentioned x, y and zsatisfy the following two inequalities.( 1/7)≦(3−x−y−z+w2)/6<(½)0<(1.5x+y−w2)/6<(9/2)

That is, in the general formula [I], “(3−x−y−z+w2)/6” represents anumerical value of 1/7 or larger and ½ or smaller.

Also in the general formula [I], “(1.5x+y−w2)/6” represents a numericalvalue of larger than 0 and smaller than 9/2.

Regarding Range of y+w1:

In the general formula [I], the number of moles of oxygen (namely, y+w1)is preferably smaller than 2, more preferably smaller than 1.7, andstill more preferably smaller than 1.5, from the standpoint of emissionintensity. On the other hand, the number of moles of oxygen (namely,y+w1) is preferably larger than 0.05, more preferably larger than 0.1,from the standpoint of ease of manufacture.

Regarding Range of w1+w2:

Furthermore, in the general formula [I], the number of moles of Al(namely, w1+w2) is usually 5 or smaller, preferably 3 or smaller, morepreferably 1 or smaller, from the standpoint of emission intensity. Thelower limit thereof is, from the standpoint of ease of manufacture,preferably close to 0, and particularly preferably 0.

Examples of Chemical Composition:

Preferable examples of the chemical composition of the above-mentionedgeneral formula [I] will be listed below. However, the crystal phasecomposition of the phosphor of the present invention (I) is not limitedto the following examples.

Preferable examples of the chemical composition of the general formula[I]′ with which oxygen is not mixed include:La_(1.37)Ce_(0.03)Ca_(2.40)Si₆N₁₁, La_(2.15)Ce_(0.10)Ca_(1.23)Si₆N₁₁,and La_(2.57)Ce_(0.03)Ca_(0.60)Si₆N₁₁. Preferable examples in whichoxygen is present include:La_(1.71)Ce_(0.1)Ca_(1.57)Si₆O_(0.44)N_(10.56),La_(1.71)Ce_(0.03)Ca_(2.20)Si₆O_(1.00)N_(10.00), andLa_(2.37)Ce_(0.03)Ca_(0.75)Si₆O_(0.30)N_(10.70).

Regarding Space Group and Powder X-Ray Diffraction Pattern of CrystalPhase:

The crystal phase represented by the above-mentioned general formula [I]is essentially a new structure (with respect to its space group and siteconstituent ratio) among alkaline-earth metal element—rare-earth metalelement (letting it “Ln”)—Si—N systems. In the following, explanationwill be given on the difference between this crystal phase and crystalphases of known substances.

The crystal phase represented by the above-mentioned general formula [I]is of P4bm or analogous space group, whereas known SrYbSi₄N₇ andBaYbSi₄N₇ are of P6₃mc space group (refer to Non-Patent Document 2) andknown BaEu(Ba_(0.5)Eu_(0.5))YbSi₆N₁₁ is of P2₁3 space group (refer toNon-Patent Document 3). In this way, the space group of the crystalphase represented by the general formula [I] is significantly differentfrom those of previously known phosphors. In addition, the powder X-raydiffraction pattern of the crystal phase represented by the generalformula [I] is significantly different from those of previously knownphosphors. This apparently indicates that they have different crystalstructures from each other since crystal phases can be examined based onthe powder X-ray diffraction patterns.

The crystal phase represented by the above-mentioned general formula [I]has a unique site constituent ratio in which the total number of cationswith smaller valence than Si, surrounded by SiN₄ tetrahedron, relativeto the number of SiN₄ tetrahedron is over 3/6. On the other hand, inknown Ce-activated La₃Si₆N₁₁, the total number of cations with smallervalence than Si, surrounded by SiN₄ tetrahedron, relative to the numberof SiN₄ tetrahedron is equal to 3/6 (refer to Patent Document 2). And,in known LnAl(Si_(6−z)Al_(z))N_(10−z)O_(z):Ce phosphor, the total numberof cations with smaller valence than Si, surrounded by Si(or Al)N(or O)₄tetrahedron, relative to the number of Si(or Al)N(or O)₄ tetrahedron isequal to 2/6 (refer to Patent Document 1). In this way, the crystalphase represented by the above-mentioned general formula [I] isapparently different from those of previously known phosphors in theconstituent ratio of each site, which characterizes the crystalstructure.

FIG. 5 shows an example (it corresponds to Example 8 to be describedlater) of powder X-ray diffraction pattern of the phosphor of thepresent invention (I). FIG. 5 shows a pattern obtained by a measurementof a cluster of particles with no orientation. In the phosphor of thepresent invention, of which crystal is tetragonal or analogous systemand space group is P4bm and analogous group, there is a tendency thatthe relative intensity of the 110 plane peak to the 001 plane peak,assuming that it is a tetragonal system, increases with increasingcontent of the A element such as Ca. It is known that the basiccomposition of crystal phase of the phosphor of the present invention(I) is Ca_(1.5x)La_(3−x)Si₆N₁₁ by an elemental analysis on a sampleobtained by washing its single phase.

This indicates that the peak intensity of the 110 plane is significantlyincreased relatively because, in the chemical formula ofCa_(1.5x)La_(3−x)Si₆N₁₁, the Ca+La site exceeds 3 (=3+0.5x) and thus asite different from La site of La₃Si₆N₁₁ phase inevitably appears.Therefore, Ca_(1.5x)La_(3−x)Si₆N₁₁ is a new crystal phase that isdifferent from La₃Si₆N₁₁ phase.

Other Points of Crystal Phase of the General Formula [I]:

In the phosphor of the present invention (I), a part of the constituentelements of the crystal phase represented by the above-mentioned formula[I] may be substituted with a defect or another kind of element, insofaras its performance is not deteriorated. Examples of the another kind ofelement are as follows.

For example, in the general formula [I], M site may be substituted withat least one kind of transition metal element or rare-earth elementselected from the group consisting of Nd, Sm, Dy, Ho, Er and Tm. Amongthem, substitution of Sm and/or Tm, which are rare-earth elements, ispreferable.

Furthermore, in the general formula [I], a part of or entire Al may besubstituted with B, for example. When the phosphor of the presentinvention (I) is produced by firing the material in a BN container, aphosphor in which Al is substituted with B as described above can beproduced. This is because B may be mixed into the resultant phosphorthen.

In addition, in the general formula [I], O and/or N sites may besubstituted with negative ions of S, Cl and/or F, for example.

Moreover, in the general formula [I], a part of Si may be substitutedwith Ge and/or C. The substitution rate is preferably 10 mole percent orlower, more preferably 5 mole percent or lower, and still morepreferably 0 mole percent.

Because no significant reduction in emission intensity occurs, each siteof R, A, Si, Al, O and N in the general formula [I] may be substitutedwith some elements in 5 mole percent or lower, or may have defects in 10mole percent or lower. However, it is preferable that both of them are 0mole percent.

At this point, it is preferable that the present phosphor (I) consistsof the crystal phase with the chemical composition of theabove-mentioned general formula [I] as a whole, in order to remarkablyachieve the advantageous effect of the present invention.

[1-2. Characteristics of Phosphor (I)]

There is no limitation on the characteristics of the phosphor of thepresent invention (I) insofar as it comprises the crystal phaserepresented by the above-mentioned general formula [I]. However, itusually has such properties as described below.

[1-2-1. Characteristics on Luminescent Color of Phosphor (I)]

The phosphor of the present invention (I) usually emits yellow to orangelight. Namely, the phosphor of the present invention (I) is usually ayellow to orange phosphor.

The color coordinates (x, y) of the fluorescence of the phosphor of thepresent invention (I) is usually within the area surrounded by (0.420,0.400), (0.420, 0.570), (0.600, 0.570), and (0.600, 0.400). It ispreferably within the area surrounded by (0.440, 0.430), (0.440, 0.530),(0.580, 0.530), and (0.580, 0.430). Accordingly, the color coordinate xof the fluorescence of the phosphor of the present invention (I) isusually 0.420 or larger, preferably 0.440 or larger, and usually 0.600or smaller, preferably 0.580 or smaller. On the other hand, the colorcoordinate y is usually 0.400 or larger, preferably 0.430 or larger, andusually 0.570 or smaller, preferably 0.530 or smaller.

The color coordinate of fluorescence can be calculated from the emissionspectrum to be described later. In this context, the above-mentionedcolor coordinates (x, y) mean those in the CIE standard colorimetricsystem of the luminescent color when excited with light having 460-nmwavelength.

[1-2-2. Characteristics on Emission Spectrum]

There is no special limitation on the spectrum (emission spectrum) ofthe fluorescence emitted by the phosphor of the present invention (I).In view of its use as yellow to orange phosphor, the wavelength ofemission peak of the emission spectrum when excited with light of 460-nmwavelength is in the range of usually 480 nm or longer, preferably 560nm or longer, more preferably 565 nm or longer, still more preferably570 nm or longer, and usually 680 nm or shorter, preferably 650 nm orshorter, more preferably 625 nm or shorter.

In addition, the full width at half maximum (full width at half maximum,hereinafter referred to as “FWHM” as appropriate) of the emission peakof the phosphor of the present invention (I), when excited with light of460-nm wavelength, is usually 130 nm or longer, preferably 140 nm orlonger, more preferably 145 nm or longer. Such a large full width athalf maximum can enhance the color rendering of the light emittingdevice or the like which uses the phosphor of the present invention (I)and a blue LED or the like in combination. In addition, since thephosphor of the present invention (I) has a sufficient emissionintensity also at longer wavelength region (namely, around 630 nm to 690nm) than that of yellow light, a warm white light can be obtained whenincorporated with a blue LED. This characteristic of the phosphor of thepresent invention (I) is much superior to that of known YAG:Ce phosphors(the FWHM of commercially available P46-Y3 is 126 nm). There is nospecial limitation on the upper limit to the full width at half maximumof the emission peak, but usually it is 280 nm or smaller.

The measurement of the emission spectrum of the phosphor of the presentinvention (I) and the calculation of its light emitting area, wavelengthof emission peak, and full width at half maximum of the peak can becarried out by, for example, using a fluorescence measurement apparatusmanufactured by JASCO corporation at a room temperature (usually, 25°C.).

[1-2-3. Excitation Wavelength]

The phosphor of the present invention (I) can be excited by lightshaving a variety of wavelengths (excitation wavelengths) depending onthe composition or the like of the phosphor of the present invention(I). It is usually excited by lights having wavelength ranges ofnear-ultraviolet region to blue region preferably. A specific range ofthe excitation wavelength is usually 300 nm or longer, preferably 340 nmor longer, and usually 500 nm or shorter, preferably 480 nm or shorter.

[1-2-4. Weight-Average Median Diameter]

It is preferable that the weight-average median diameter of the phosphorof the present invention (I) is in the range of usually 0.1 μm orlarger, preferably 0.5 μm or larger, and usually 30 μm or smaller,preferably 20 μm or smaller. When the weight-average median diameter istoo small, the brightness tends to decrease and the phosphor particlestend to aggregate. On the other hand, when the weight-average mediandiameter is too large, unevenness in coating, clogging in a dispenser,and the like tend to occur.

[1-2-5. Chemical Resistance]

The phosphor of the present invention (I) is also superior in chemicalresistance usually. For example, in the phosphor of the presentinvention (I), the crystal phase represented by the above-mentionedgeneral formula [I] is not dissolved in aqua regia, an extremely strongagent in acid strength, and it can emit a fluorescence even afterimmersed in aqua regia. Therefore, the phosphor of the present invention(I) can be used under a variety of environments, which is highly usefulindustrially.

[1-2-6. Temperature Characteristics]

The phosphor of the present invention (I) is also superior intemperature characteristics usually. Specifically, the ratio of themaximum emission peak intensity value at 130° C. in the emissionspectral map relative to the maximum emission peak intensity value at25° C. is usually 60% or more, preferably 65% or more, and particularlypreferably 70% or more, when irradiated with a light having wavelengthof 455 nm.

Furthermore, though this ratio of usual phosphors rarely exceeds 100%because its emission intensity decreases with increasing temperature, itcan exceed 100% for some reason. However, over 150% of that ratio tendsto lead to color shift due to the temperature change.

The above-mentioned temperature characteristics can be examined asfollows, for example, using an emission spectrum measurement device ofmulti-channel spectrum analyzer, MCPD7000, manufactured by OtsukaElectronics Co., Ltd., a stage equipped with a cooling mechanism using apeltiert device and a heating mechanism using a heater, and a lightsource device equipped with a 150-W xenon lamp.

A cell holding the phosphor sample is put on the stage, and thetemperature is changed within the range from 20° C. to 180° C. Afterverifying the surface temperature of the phosphor is held at 25° C. or130° C., the emission spectrum of the phosphor is measured when it isexcited with a light from the light source having wavelength of 455 nm,which is separated using a diffraction grating. Then the emission peakintensity can be decided from the measured emission spectrum. At thispoint, as the measurement value of the surface temperature of thephosphor on the side irradiated with the excitation light, is used avalue corrected by the temperature values measured with a radiationthermometer and a thermocouple.

[1-2-7. Quantum Efficiency]

The external quantum efficiency of the phosphor of the present invention(I) is usually 30% or higher, preferably 35% or higher, more preferably40% or higher, and particularly preferably 43% or higher. The higher theexternal quantum efficiency is, the more preferable, for designing alight emitting device with high emission intensity.

The internal quantum efficiency of the phosphor of the present invention(I) is usually 35% or higher, preferably 40% or higher, more preferably45% or higher, and still more preferably 50% or higher. In this context,internal quantum efficiency means the ratio of the number of emittedphotons to the number of photons in the excitation light that isabsorbed into the phosphor. When the internal quantum efficiency is low,the emission efficiency tends to decrease.

Also, the higher the absorption efficiency of the phosphor of thepresent invention (I) is, the more preferable. It is usually 70% orhigher, preferably 75% or higher, and more preferably 80% or higher.Since external quantum efficiency is calculated as the product ofinternal quantum efficiency and absorption efficiency, the higher theabsorption efficiency is, the more preferable, for higher externalquantum efficiency.

(Method for Measuring Absorption Efficiency, Internal Quantum Efficiencyand External Quantum Efficiency)

In the following, methods for determining the absorption efficiencyα_(q), internal quantum efficiency η_(i) and external quantum efficiencyη_(o) of a phosphor will be described.

First, the phosphor sample to be measured (for example in a state ofpowder or the like) is stuffed up in a cell with its surface smoothedsufficiently to keep high measurement accuracy, and then it is set on acondenser such as an integrating sphere. The reason for using acondenser such as an integrating sphere is to count up all the photonsboth reflected at and emitted, by a fluorescence phenomenon, from thephosphor sample. In other words, it is to prevent the failure incounting photons going out of the measurement system.

A light emission source for exciting the phosphor is attached on thecondenser such as an integrating sphere. This light emission source, anXe lamp for example, is adjusted using a filter, monochromator (gratingmonochromator) or the like so that the wavelength of emission peakthereof will be that of a monochromatic light of, for example, 455-nmwavelength. Then the spectrum including those of emitted light(fluorescence) and reflected light is measured, using a spectrometer,such as MCPD2000 or MCPD7000 manufactured by Otsuka Electronics Co.,Ltd., for example, by irradiating the phosphor sample to be measuredwith the light from the light emission source, of which wavelength ofemission peak is adjusted. The light, of which spectrum is to bemeasured here, actually includes, among lights (excitation lights) fromthe excitation light source, reflected lights that are not absorbed inthe phosphor and lights (fluorescences) having the other wavelengthsthat are emitted by a fluorescence phenomenon from the phosphor whichabsorbed the excitation light. Namely, the region close to theexcitation light corresponds to the reflection spectrum, and the regionof which wavelengths are longer the reflection corresponds to thefluorescence spectrum (occasionally referred to as “emission spectrum”).

Absorption efficiency α_(q) takes the value obtained through dividingN_(abs) by N, where N_(abs) is the number of photons of the excitationlight that is absorbed in the phosphor sample and N is the number of allthe photons in the excitation light.

First, the latter one, the total number N of all the photons in theexcitation light is determined as follows. That is, the reflectionspectrum I_(ref)(λ) is measured using the spectrometer with respect to asubstance to be measured having reflectance R of approx. 100% to theexcitation light, such as a reflection plate “Spectralon” manufacturedby Labsphere (with 98% of reflectance R to an excitation light of 400-nmwavelength), which is attached to the above condenser such as anintegrating sphere in the same disposition as the phosphor sample. Thevalue in the following (formula a), calculated from this reflectionspectrum I_(ref)(λ), is proportional to N.

$\begin{matrix}\lbrack {{Mathematical}{\mspace{11mu}\;}{Formula}{\mspace{11mu}\;}1} \rbrack & \; \\{\frac{1}{R}{\int{{\lambda \cdot {I_{ref}(\lambda)}}{\mathbb{d}\lambda}}}} & ( {{formula}\mspace{14mu} a} )\end{matrix}$

The integration of the formula may be performed at only such intervalsthat I_(ref)(λ) takes a substantially significant value. The numberN_(abs) of the photons in the excitation light that is absorbed in thephosphor sample is proportional to the amount calculated in thefollowing (formula b).

$\begin{matrix}\lbrack {{Mathematical}{\mspace{11mu}\;}{Formula}{\mspace{11mu}\;}2} \rbrack & \; \\{{\frac{1}{R}{\int{{\lambda \cdot {I_{ref}(\lambda)}}{\mathbb{d}\lambda}}}} - {\int{{\lambda \cdot {I(\lambda)}}{\mathbb{d}\lambda}}}} & ( {{formula}\mspace{14mu} b} )\end{matrix}$

Here, the function I(λ) is a reflection spectrum when the targetphosphor sample, of which absorption efficiency α_(q) is intended to bedetermined, is attached. The integration interval in (formula b) is setto be the same as in (formula a). By restricting the integrationinterval as above, the second term in (formula b) becomes correspondingto the number of photons emitted from the measurement object, phosphorsample, by the reflection of the excitation light. In other words, itbecomes corresponding to the number of all photons emitted from themeasurement object, phosphor sample, except for the number of photonsemitted by the fluorescence phenomenon. Since the actual measurementvalue of the spectrum is generally obtained as digital data which aredivided by a certain finite band width relating to λ, the integrationsof (formula a) and (formula b) are calculated as finite sum based on theband width.

Consequently, α_(q) can be calculated as α_(q)=N_(abs)/N=(formulab)/(formula a).

Next, a method for determining internal quantum efficiency η_(i) will bedescribed. The internal quantum efficiency η_(i) takes the valueobtained through dividing N_(abs) by N, where N_(PL) is the number ofphotons originating from the fluorescence phenomenon and N_(abs) is thenumber of photons absorbed in the phosphor sample.

Here, N_(PL) is proportional to the amount calculated by the following(formula c).[Mathematical Formula 3]∫λ·I(λ)dλ  (formula c)

At this point, the integration interval is restricted to the wavelengthregion of photons that are originating from the fluorescence phenomenonof the phosphor sample. This is because contribution of the photonsreflected from the phosphor sample should be eliminated from I(λ).Specifically, the lower limit of the integration interval in (formula c)takes the value of upper limit of the integration interval in (formulaa), and the upper limit thereof takes the value that is necessary andsufficient for including the photons originating from the fluorescence.

Consequently, the internal quantum efficiency can be calculated asη_(i)=(formula c)/(formula b).

Incidentally, the integration from spectra expressed by digital data canbe carried out in the same way as when absorption efficiency α_(q) iscalculated.

The external quantum efficiency η_(o) can be decided as a product of theabsorption efficiency α_(q) and internal quantum efficiency η_(i), whichare obtained as above. In another way, it can be determined using arelation of η_(o)=(formula c)/(formula a). η_(o) takes the valueobtained through dividing N_(PL) by N, where N_(PL) is the number ofphotons originating from the fluorescence and N is the number of totalphotons in the excitation light.

[1-3. Advantageous Effects of Phosphor of Present Invention (I)]

As described above, the phosphor of the present invention (I) containsmuch red light component and can emit lights having large full width athalf maximums. Namely, the emission intensity of the phosphor of thepresent invention (I) is sufficient at red, longer wavelength region,and the emission spectrum thereof shows an emission peak withsignificantly large full width at half maximum. Accordingly, when thephosphor of the present invention (I) is used for a white light emittingdevice, the white light emitting device can emit warm white light withhigh color rendering.

In addition, the phosphor of the present invention (I) can be excitedparticularly efficiently by a near-ultraviolet or blue semiconductorluminous element and emit yellow to green fluorescence, usually.

Furthermore, in the phosphor of the present invention (I), there isusually less reduction in emission efficiency associated withtemperature rising than YAG:Ce phosphors, which have been frequentlyused for white light emitting devices conventionally.

[1-4. Use of Phosphor of Present Invention (I)]

There is no limitation on the use of the phosphor of the presentinvention (I). However, it can be used preferably for illuminatingdevices, displays or the like for example, making use of theabove-mentioned advantageous effects. Among them, it is fit forrealizing high-power LED lamps for general lighting and particularly fitfor warm white LEDs with high brightness, high color rendering, andrelatively low color temperature. In addition, since the phosphor of thepresent invention (I) shows less decrease in emission efficiencyaccompanying temperature rising as described above, light emittingdevices using the phosphor of the present invention (I) can exhibit highemission efficiency, less decrease in emission efficiency accompanyingtemperature rising, high brightness, and broad range of colorreproduction.

The phosphor of the present invention (I) can be used preferably forvarious light emitting devices (for example, for “light emitting devicesof the present invention” to be described later), particularly makingthe most of such characteristics that it can be excited by a blue lightor a near-ultraviolet light. In that case, by adjusting the kind orcontent of the phosphors used together, light emitting devices havingvarious luminescent colors can be produced. Among them, a combined useof an excitation light source emitting blue light with the phosphor ofthe present invention (I), which is usually a yellow to orange phosphor,can realize a white light emitting device. In this case, even anemission spectrum that is similarly to so-called pseudo-white (which isthe luminescent color of light emitting devices having a blue LED and aphosphor emitting yellow fluorescence (namely, yellow phosphor) incombination, for example) can be obtained.

Furthermore, by adding a red phosphor and, if necessary, a greenphosphor to the above-mentioned white light emitting device, a lightemitting device that is extremely excellent in red color rendering orthat can emit a warm white light can be realized. When using anear-ultraviolet excitation light source, adding a blue phosphor, redphosphor and/or a green phosphor for adjusting the luminous wavelengthin addition to the phosphor of the present invention (I) properly canrealize white light sources with desirable luminescent colors.

The luminescent color of the light emitting device is not limited towhite. For example when the phosphor of the present invention (I) isused as wavelength conversion material, light emitting devices emittingany color of light can be realized by adding other phosphors or the liketo the phosphor of the present invention (I) for adjusting the kind orcontent of the phosphors. The light emitting devices thus obtained canbe used for illuminating devices or illuminant portions (especially,back-lightings of liquid crystal displays) of displays.

Preferable examples of the above-mentioned other phosphor include:phosphors emitting blue, blue green, green, yellow green, red or deepred light. It is particularly preferable to use a blue light emittingdiode, as excitation light source, and a green or red phosphor incombination with the phosphor of the present invention (I), because itcan realize a white light emitting device. Moreover, a desirable whitelight emitting device can be realized also by using a near-ultravioletlight emitting diode and a blue phosphor, a red phosphor, and a greenphosphor in combination with the phosphor of the present invention (I).By adding a red to deep red phosphor to these white light emittingdevices, the color rendering thereof can be further enhanced.

[2. Production Method of Phosphor (I)]

There is no limitation on the production method of the phosphor of thepresent invention (I); any method can be used. For example, it can beproduced by mixing phosphor precursors (mixing step), which wereprepared as the raw materials, and firing the mixed phosphor precursors(firing step). In the following, such a production method (hereinafterreferred to as “the production method (I) according to the presentinvention” as appropriate) will be described as an example of theproduction method of the phosphor of the present invention (I).

[2-1. Preparation of Phosphor Precursors]

Phosphor precursors including material of the M (hereinafter referred toas “M source” as appropriate), material of the R (hereinafter referredto as “R source” as appropriate), material of the A (hereinafterreferred to as “A source” as appropriate), material of Si (hereinafterreferred to as “Si source” as appropriate), material of Al (hereinafterreferred to as “Al source” as appropriate), material of O (hereinafterreferred to as “O source” as appropriate), and material of N(hereinafter referred to as “N source” as appropriate) of theaforementioned formula [I] are prepared.

Examples of the M source, R source, A source, Si source and Al sourceused in the production method (I) according to the present inventioninclude: nitrides, nitrogen-containing compounds such as Si(NH)₂,oxides, hydroxides, carbonates, nitrates, sulfates, sulfides, oxalates,carboxylates, halides or the like of each of these M, R, A, Si and Al.Appropriate ones can be selected from these compounds depending on thekind of the firing atmosphere such as nitrogen, hydrogen-containingnitrogen, ammonia, argon or the like.

Examples of the M source can be listed as follows in terms of kinds ofM.

Among the above-mentioned M source, examples of the Ce source include:CeO₂, Ce₂(SO₄)₃, hydrate of Ce₂(C₂O₄)₃, CeCl₃, CeF₃, hydrated ofCe(NO₃)₃, CeN and the like. Among them, CeO₂ and CeN are preferable.

Examples of the Eu source include: Eu₂O₃, Eu₂(SO₄)₃, Eu₂(C₂O₄)₃·10H₂O,EuCl₂, EuCl₃ and Eu(NO₃)₃.6H₂O, EuN, EuNH and the like. Among them,Eu₂O₃, EuCl₂, and the like are preferable. Eu₂O₃ is particularlypreferable.

Examples of the raw materials of activator elements such as Mn source,Yb source, Pr source, Tb source or the like include: those compoundslisted as the examples of the Eu source in which Eu is replaced by Mn,Yb, Pr, Tb or the like, respectively.

Examples of the R source can be listed as follows in terms of kinds ofR.

Namely, examples of the La source of the R source include: lanthanumnitride, lanthanum oxide, lanthanum nitrate, lanthanum hydroxide,lanthanum oxalate, and lanthanum carbonate. Of these, lanthanum nitrideis preferable.

Examples of the Gd source of the R source include: gadolinium nitride,gadolinium oxide, gadolinium nitrate, gadolinium hydroxide, gadoliniumoxalate, and gadolinium carbonate.

In addition, examples of the Lu source of the R source include: lutetiumnitride, lutetium oxide, lutetium nitrate, and lutetium oxalate.

Examples of the Y source of the R source include: yttrium nitride,yttrium oxide, yttrium nitrate, yttrium oxalate, and yttrium carbonate.

Further, examples of the Sc source of the R source include: scandiumnitride, scandium oxide, scandium nitrate, and scandium oxalate.

Examples of the A source can be listed as follows in terms of kinds ofA.

Namely, examples of the Ba source of the A source include: BaSiN₂,Ba₃N₂, barium carbonate, barium hydroxide, barium oxide, barium nitrate,barium acetate, and barium oxalate. Of these, BaSiN₂ and Ba₃N₂ arepreferable.

Examples of the Sr source include: SrSiN₂, Sr₃N₂, strontium carbonate,strontium hydroxide, strontium oxide, strontium nitrate, strontiumacetate, and strontium oxalate. Of these, SrSiN₂ and Sr₃N₂ arepreferable.

In addition, examples of the Ca source of the A source include: CaSiN₂,Ca₃N₂, calcium carbonate, calcium hydroxide, calcium oxide, calciumnitrate, calcium acetate, and calcium oxalate. Of these, CaSiN₂ andCa₃N₂ are preferable.

Examples of the Mg source of the A source include: MgSiN₂, Mg₃N₂, basicmagnesium carbonate, magnesium oxide, magnesium nitrate, magnesiumacetate, and magnesium oxalate. Of these, MgSiN₂ and Mg₃N₂ arepreferable.

In addition, examples of the Zn source of the A source include: Zn₃N₂,zinc carbonate, zinc hydroxide, zinc oxide, zinc nitrate, zinc acetate,and zinc oxalate. Of these, Zn₃N₂ is preferable.

Examples of the Si source include: CaSiN₂, Si₃N₄, SiO₂, H₄SiO₄, Si(NH)₂,and Si(OCOCH₃)₄. Of these, CaSiN₂ and Si₃N₄ are preferable.

Regarding Si₃N₄, from the standpoint of reactivity, ones of smallparticle diameters are preferable, and from the standpoint of emissionefficiency, ones with high purity are preferable. Further from thestandpoint of emission efficiency, β-Si₃N₄ is more preferable thanα-Si₃N₄, and ones containing less carbon atoms, which are impurities,are particularly preferable. The smaller the content of the carbon atomsis, the more preferable. However, it is usually 0.01 weight % or more,and usually 0.3 weight % or less, preferably 0.2 weight % or less, morepreferably 0.1 weight % or less, still more preferably 0.05 weight % orless, particularly preferably 0.03 weight % or less. When the content ofcarbon is large, the host crystals tend to color. When the host crystalscolor, the internal quantum efficiency tends to decrease. However, whenusing β-silicon nitride containing less carbon atoms such as describedabove, the internal quantum efficiency and thus the brightness willimprove due to reduced coloration of the host crystals.

Examples of the Al source include: AlN, CaAlSiN₃, AlON, Al₂O₃, Al,aluminium hydroxide, and aluminium nitrate.

In addition, examples of the R source, A source, Si source, Al source,and M source include: respective metal R, A, Si, Al, and M, and alloysof them.

An example of the N source is nitrogen from the atmosphere such ashydrogen-containing nitrogen atmosphere or ammonia which is used whenproducing the phosphor of the present invention (I). In that case, allof the above-mentioned compounds can be used as the R source, A source,Si source, Al source and M source respectively, but it is preferable touse nitrogen-containing compounds of the above-mentioned ones for them.

Or otherwise, nitrogen-containing compounds of the above-mentioned Rsource, A source, Si source, Al source, and M source examples can beused as the N source, when the phosphor of the present invention (I) isproduced in a nitrogen atmosphere at a pressure of about 10 atmospheresor an argon atmosphere.

Furthermore, nitrogen gas can be used as the nitrogen source, when thephosphor of the present invention (I) is produced in a nitrogenatmosphere at such a high pressure as far beyond 10 and 2000 or loweratmospheres. In this case, respective metal R, A, Si, Al, and M, andalloys of them can be used for example as the R source, A source, Sisource, Al source, and M source. The nitrogen pressure in this case ispreferably 40 atmospheres or higher, and more preferably 80 atmospheresor higher from the standpoint of emission intensity. In view of ease inindustrial production, it is preferably 500 atmospheres or lower, andmore preferably 200 atmospheres or lower.

Examples of the O source include oxygen-containing compounds of theabove-mentioned R source, A source, Si source, Al source, and M source.

Each of the M sources, R sources, A sources, Si sources, Al sources, Osources and N sources can be used either as a single kind thereof or astwo or more kinds of them in any combination and in any ratio. A certainphosphor precursor can be two or more of the M source, R source, Asource, Si source, Al source, O source or N source at the same time.

Of the above-mentioned various phosphor precursors, it is preferable touse ones of high purity with a high degree of whiteness in order toheighten the emission efficiency of the resultant phosphor (I).Specifically, it is preferable to use phosphor precursors whosereflectances in the wavelength region of from 380 nm to 780 nm are 60%or higher, preferably 70% or higher, more preferably 80% or higher. Inparticular, at 525 nm, which is close to the wavelength of emission peakof the phosphor of the present invention (I), the reflectances of thephosphor precursors are preferably 60% or higher, more preferably 70% orhigher, still more preferably 80% or higher, particularly preferably 90%or higher.

Of all the plurality of phosphor precursors, Si₃N₄ in particular ispreferably of high reflectance. As Si₃N₄ having such reflectance, thosewhose contents of carbon atoms, which are contained as impurities, arewithin the above-mentioned range can be used.

The reflectance can be determined by measuring reflectance spectrum. Themethod of measurement is the same as what is described for thepreviously-mentioned absorption efficiency, internal quantum efficiencyand external quantum efficiency.

Of the impurities contained in the phosphor precursors, each content ofFe, Co, Cr or Ni in the phosphor precursor is usually 1000 ppm or lower,preferably 100 ppm or lower, more preferably 50 ppm or lower, still morepreferably 10 ppm or lower, and particularly preferably 1 ppm or lower.

In addition, the oxygen concentration in each phosphor precursor isusually 1000 ppm or lower, preferably 100 ppm or lower, more preferably50 ppm or lower, still more preferably 10 ppm or lower, and particularlypreferably 1 ppm or lower.

The weight-average median diameter (D₅₀) in each phosphor precursor isusually 0.1 μm or larger, preferably 0.5 μm or larger, and usually 30 μmor smaller, preferably 20 μm or smaller, more preferably 10 μm orsmaller, still more preferably 3 μm or smaller. For that purpose,pulverization may be carried out preliminarily with a dry-typepulverizer such as a jet mill depending on the kind of the phosphorprecursor. In this way, each phosphor precursor is dispersedhomogenously in the mixture and the reactivity of the solid statereaction of the mixture can be heightened due to increased surface areaof the phosphor precursor, thereby making it possible to inhibitimpurity phase generation. Particularly for a nitride phosphorprecursor, it is preferable to use one having smaller particle diameterthan the other kind of phosphor precursors from the standpoint ofreactivity.

For a phosphor precursor with deliquescence, it is preferable to useanhydrides.

[2-2. Mixing Step]

The phosphor precursors are weighed out so as to give desiredcomposition, mixed well, transferred to a container such as a crucible,and fired at a predetermined temperature in a predetermined atmosphere.The phosphor of the present invention (I) can be obtained by pulverizingand washing the fired product.

No particular limitation is imposed on the method of mixing the Msource, R source, A source, Si source, Al source, O source and N source.The examples include the following methods (A) and (B).

-   (A) Dry-type mixing methods in which the phosphor precursors such as    M source, R source, A source, Si source, Al source, O source and N    source are pulverized and mixed by combining pulverization, which is    done by means of a dry-type pulverizer such as a hammer mill, roll    mill, ball mill and jet mill, or pestle/mortar, and mixing, which is    done by means of a mixing apparatus such as ribbon blender, V type    blender and Henschel mixer, or pestle/mortar.-   (B) Wet-type mixing method in which solvent or dispersion medium    such as water is added to the phosphor precursors such as M source,    R source, A source, Si source, Al source, O source and N source, and    mixing is done by means of a pulverizer, pestle/mortar or    evaporation dish/stirring rod, to make a solution or slurry,    followed by drying by such method as spray drying, heated drying or    air drying. It is difficult to use this method for phosphor    precursors that can not be present stably as a solution.

Concerning various conditions for those mixing methods, knownconditions, such as using two kinds of balls having different particlediameters mixed in a ball mill, can be selected as appropriate.

The phosphor precursors are mixed preferably within an N₂ glove box withcontrolled moisture content using a mixer in order not to deterioratethe nitride material due to moisture. The moisture content of theworkplace for mixing is usually 10000 ppm or lower, preferably 1000 ppmor lower, more preferably 10 ppm or lower, and still more preferably 1ppm or lower. The oxygen content of the same workplace is usually 1 ppmor lower, preferably 10000 ppm or lower, more preferably 1000 ppm orlower, still more preferably 100 ppm or lower, and particularlypreferably 10 ppm or lower.

The phosphor precursors may be sieved at the time of above-mentionedmixing if necessary. In such a case, various kinds of commerciallyavailable sieves can be used. However, sieves made of a resin such asnylon mesh are more preferable than those of metal mesh for preventingcontamination with impurities.

In addition, it is preferable that nitrides are dispersed homogenouslyin the mixture of the phosphor precursors in that case so as to enhancereactivity of the solid state reaction of the mixture and preventimpurity phases from generating. In order to carry out it specifically,for example, phosphor precursors other than the nitrides are mixed,fired and pulverized preliminarily, followed by mixing the nitrides andfiring the mixture. Using nitrides that are preliminarily pulverizedwith a dry-type pulverizer such as a jet mill as a phosphor precursor isparticularly preferable because the surface areas of the nitride powdersare increased and thus the reactivity of the solid state reaction of thenitrides is enhanced. The methods exemplified above may be employedsingly, but preferably they are employed in some combination.

[2-3. Firing Step]

The firing step is usually done by filling the mixture of the phosphorprecursors such as M source, R source, A source, Si source, Al source, Osource and N source obtained in the above-mentioned mixing step into aheat-resistant vessel such as a crucible or a tray which is made ofmaterial unlikely to react with each phosphor precursor and firing them.

Material examples of such heat-resistant vessels used for such a firingstep include: ceramics such as alumina, quartz, boron nitride, siliconnitride, silicon carbide, magnesium and mullite; metals such asplatinum, molybdenum, tungsten, tantalum, niobium, iridium and rhodium;alloys mainly constituted of these metals; and carbon (graphite).

Among them, heat-resistant vessels made of boron nitride, alumina,silicon nitride, silicon carbide, platinum, molybdenum, tungsten, ortantalum are preferable. Ones made of boron nitride or molybdenum ismore preferable. Particularly preferable are alumina ones that arestable even at firing temperatures in a nitrogen-hydrogen reducingatmosphere. However, when using phosphor precursors which react withalumina, boron nitride heat-resistant vessels can be preferably used.

The filling rates (hereinafter referred to as “filling rate intoheat-resistant vessel”) at which the phosphor precursors are filled intothe above-mentioned heat-resistant vessels differ depending on thefiring condition or the like. However, the rate may be such that thepulverization of the fired product will not be difficult at thepost-treatment steps to be described later. Therefore, it is usually 10volume % or larger, and usually 90 volume % or smaller. Meanwhile, thereare gaps between the particles of the phosphor precursors filled in acrucible. The volume of the phosphor precursors themselves per 100 ml inwhich the phosphor precursors are filled is usually 10 ml or larger,preferably 15 ml or larger, more preferably 20 ml or larger, and usually50 ml or smaller, preferably 40 ml or smaller, more preferably 30 ml orsmaller.

When a large amount of phosphor precursors is treated at one time, it ispreferable to make heat distributed uniformly within the heat-resistantvessel for example by decelerating the temperature rising rate.

The filling rate (hereinafter referred to as “filling rate into furnace”as appropriate) at which the heat-resistant vessels are filled into afurnace is preferably such that the heat-resistant vessels will beheated in the furnace uniformly.

When a large number of heat-resistant vessels are fired in the firingfurnace, it is preferable to distribute heat uniformly to eachheat-resistant vessel, for example by decelerating the above-mentionedtemperature rising rate, for the uniformity of firing.

There is no limitation on the firing temperature (the maximum heatingtemperature) insofar as the phosphor of the present invention (I) can beobtained. However, it is usually 1300° C. or higher, preferably 1700° C.or higher, more preferably 1800° C. or higher, and usually 2300° C. orlower, preferably 2200° C. or lower. When the firing temperature is toolow or too high, generation of the crystal phase of the presentinvention tends to be difficult. Meanwhile, when the nitrogen containedin the atmosphere gas is used as the N source of the phosphor (I) asdescribed earlier, the firing temperature is usually 1300° C. or higher,preferably 1400° C. or higher, more preferably 1450° C. or higher, andusually 2300° C. or lower, preferably 2200° C. or lower.

A part of firing treatment is preferably carried out under a reducedpressure condition on the way of temperature rising. Specifically, thereduced pressure condition (specifically, 10⁻² Pa or higher and 0.1 MPaor lower as usual) is preferably provided at a certain point of time atthe temperature that is preferably the room temperature or higher, andpreferably 1500° C. or lower, more preferably 1200° C. or lower, stillmore preferably 1000° C. or lower. Particularly, it is preferable toperform the temperature rising with an inert gas or reducing gas, to bedescribed later, introduced in the system after reducing the pressure inthe system.

During the pressure reduction, the temperature may be retained ifnecessary at a desired value for 1 minute or longer, preferably 5minutes or longer, and more preferably 10 minutes or longer. The upperlimit of the retention period is usually 5 hours or shorter, preferably3 hours or shorter, and more preferably 1 hour or shorter.

The pressure at the time of firing varies depending on the firingtemperature or the like; however, it is usually the normal pressure inthe interest of convenience and facilitation. However, it is usually 3atmospheres or higher, preferably 4 atmospheres or higher, and morepreferably 8 atmospheres or higher, when the firing atmosphere isnitride.

The firing time (retention period at the maximum heating temperature)depends on the temperature or pressure at the time of firing. However,it is in the range of usually 10 minutes or longer, preferably 1 hour orlonger, and usually 24 hours or shorter, preferably 10 hours or shorter.It is preferable to decide whether the evacuation of the furnace isnecessary before firing or not in light of properties of the rawmaterials.

There is no special limitation on the atmosphere at the time of firinginsofar as the phosphor of the present invention (I) can be obtained;however, it is preferable that the firing is carried out in anatmosphere with low oxygen concentration. This is because the content ofthe oxygen in the resultant phosphor (I) can be controlled then. Theoxygen concentration at the time of firing is preferably 100 ppm orlower, more preferably 50 ppm or lower, and particularly preferably 20ppm or lower. It is ideally preferable that no oxygen exists. It ispreferable that the atmosphere used for firing is selected appropriatelyin accordance with the kind of the materials. Examples thereof include:inert gases such as mixed gas of nitrogen and hydrogen, ammonia gas,argon, carbon monoxide, carbon dioxide; and mixed gases in which two ormore kind of them are mixed. Among them, nitrogen gas or mixed gas ofnitrogen and hydrogen is preferable.

As the above-mentioned nitrogen (N₂) gas, it is preferable that the onewith the purity of 99.9% or higher is used.

When a hydrogen gas is used, the hydrogen content in the atmosphere ispreferably 1 volume % or larger, more preferably 2 volume % or larger,and preferably 5 volume % or smaller. This is because, when the contentof hydrogen in the atmosphere is too high, safety may not be guaranteed,and when it is too low, sufficient reducing atmosphere may not besecured.

The above-mentioned atmosphere gas can be introduced either beforestarting the temperature rising or in the course of the temperaturerising. Or otherwise, it can be introduced at the firing temperature. Itis particularly preferable to introduce it before or in the course ofthe temperature rising. When the firing is carried out under a flow ofsuch an atmosphere, the flow rate is usually 0.1 L/min to 10 L/min.

In addition, it is preferable that the phosphor precursors are treatedin an atmosphere containing less moisture or oxygen in the steps beforethe firing for example from weighing each phosphor precursor to fillingthe phosphor precursors into a crucible or the like, from the standpointof controlling the oxygen content of the phosphor (I).

When a large number of firing vessels are fired in the firing furnace inthe above-mentioned firing step, it is preferable to distribute heatuniformly to each firing vessel, for example by decelerating theabove-mentioned temperature rising rate, in the interest of uniformityof firing.

When carbon monoxide or cyanide is generated as a by-product in thefiring, it is preferable to replace the gas in the firing furnace withnitrogen or another inert gas while the temperature decreases aftercompleting the firing. In the course of temperature decrease, a step maybe provided where a specific temperature is retained, if necessary.

The firing may be carried out either in one step or in two or more stepsseparately. For example, it may be divided into the primary firing andthe secondary firing. In such a case, the mixture of materials obtainedin the mixing step may be subjected to the primary firing first, andafter pulverized using a ball mill or the like, subjected to thesecondary firing. It is preferable to perform the secondary firing asappropriate because the emission intensity may be enhanced by performingthe secondary firing. The conditions of the secondary firing can bedecided in the same way as the above-mentioned firing conditions ingeneral. However, the firing temperature (maximum heating temperature)is preferably lower than that of the primary firing.

[2-4. Flux]

In the firing step, flux may be added to the reaction system in order tosecure growth of good quality crystals. No particular limitation isimposed on the kind of flux. The examples include: ammonium halides suchas NH₄Cl and NH₄F.HF; alkali metal carbonates such as Na₂CO₃ and LiCO₃;alkali metal halides such as LiCl, NaCl, KCl, CsCl, LiF, NaF, KF andCsF; alkaline-earth metal halides such as CaCl₂, BaCl₂, SrCl₂, CaF₂,BaF₂, SrF₂, MgCl₂ and MgF₂; alkaline-earth metal oxides such as BaO;boron oxides such as B₂O₃, H₃BO₃ and NaB₄O₇; boric acid and boric acidsalts of alkali metals or alkaline-earth metals; phosphates such asLi₃PO₄ and NH₄H₂PO₄; aluminum halides such as AlF₃; zinc compounds suchas zinc halides like ZnCl₂ and ZnF₂, and zinc oxides; compounds of the15th group elements of the periodic table such as Bi₂O₃; and nitrides ofalkali metals, alkaline earth metals or the 13th group elements such asLi₃N, Ca₃N₂, Sr₃N₂, Ba₃N₂ and BN. Other examples of the flux include:halides of rare-earth elements such as LaF₃, LaCl₃, GdF₃, GdCl₃, LuF₃,LuCl₃, YF₃, YCl₃, ScF₃, and ScCl₃; and oxides of rare-earth elementssuch as La₂O₃, Gd₂O₃, Lu₂O₃, Y₂O₃, and Sc₂O₃. Of these, halides arepreferable. Particularly preferable are alkali metal halides,alkaline-earth metal halides, Zn halides, and rare-earth elementhalides. Of these halides, fluorides and chlorides are preferable. Forthe above-mentioned fluxes with deliquescence, it is preferable to usetheir anhydrides.

These fluxes can be used either as a single one or as a mixture of twoor more kinds in any combination and in any ratio.

When the phosphor (I) is produced by multiple firing (namely, multiplesteps of firing), the flux may be added at the primary firing or thesecondary firing. However, it is preferable to add it at the secondaryfiring. Particularly for fluxes with deliquescence, it is preferable toadd it in a firing step as late as possible.

The amount of flux used differs depending on the kind of the materialsor compounds used as the flux. It is preferably in the range of usually0.01 weight % or more, preferably 0.1 weight % or more, more preferably0.3 weight % or more, and usually 20 weight % or less, preferably 5weight % or less, relative to the entire raw materials. When the amountof the flux used is too small, the effect of flux may not be exhibited.When the amount of the flux used is too large, the effect of flux may besaturated, or it may be taken up into the host crystals, leadingpossibly to change in the luminescent color, decrease in the brightness,and deterioration of the firing furnace.

[2-5. Post-Treatment]

Steps other than described above can be carried out in the productionmethod (I) according to the present invention if necessary. For example,a pulverization step, washing step, classification step, surfacetreatment step, drying step or the like can be carried out if necessaryafter the above-mentioned firing step.

Pulverization Step

In the pulverization step, pulverizers such as a hammer mill, roll mill,ball mill, jet mill, ribbon blender, V type blender, and Henschel mixer,or pestle/mortar can be used, for example. For the sake of, for example,crushing the secondary particles while preventing destruction of thephosphor crystals generated, it is preferable to perform a ball millingusing, for example, a container made of alumina, silicon nitride, ZrO₂,glass or the like and balls made of the same material as the container,iron-core urethane, or the like in the container for on the order of 10minutes to 24 hours. In this case, a dispersant such as an organic acidor a alkaline phosphate like hexametaphosphate can be used at 0.05weight % to 2 weight %.

Washing Step

Washing can be done using, for example, water such as deionized water,organic solvent such as ethanol, or alkaline aqueous solution such asammonia water. Further, water solutions of inorganic acids such ashydrochloric acid, nitric acid, sulfuric acid, aqua regia, or a mixtureof hydrofluoric acid and sulfuric acid; or water solutions of organicacids such as acetic acid can be used, for example for the purpose ofremoving an impurity phase, such as the flux used, attached to thephosphor and improving the luminescent characteristics. The phosphor ofthe present invention (I) tends to be removed of the impurity phaseefficiently and improved in the emission intensity by washing it with astrong acid such as aqua regia. In such a case, it is preferable that,after washing with an acidic aqueous solution, an additional washingwith water is carried out.

It is preferable to perform washing to the extent that the pH of thesupernatant fluid obtained by dispersing the fired product, afterwashing it, in water which is 10 times as heavy as the phosphor andleaving it to stand for 1 hour becomes neutral (pH of around 5 to 9).This is because a deviation toward basicity or acidity of theabove-mentioned supernatant fluid may adversely affect the liquid mediumto be described later or the like when the phosphor is mixed with theliquid medium.

The above-mentioned degree of washing can also be indicated by theelectric conductivity of the supernatant fluid that is obtained bydispersing the washed phosphor in water which is 10 times as heavy asthe phosphor and leaving it to stand for 1 hour. The lower the electricconductivity is, the more preferable, from the standpoint of higherluminescent characteristics. However, also in consideration of theproductivity, it is preferable to repeat the washing treatments untilthe electric conductivity is usually 10 mS/m or lower, preferably 5 mS/mor lower, and more preferably 4 mS/m or lower.

The method for measuring the electric conductivity is as follows. Thephosphor particles, which have larger specific gravity than water, areallowed to precipitate spontaneously, by leaving them to stand for 1hour after they are stirred for dispersion in water which is 10 times asheavy as the phosphor for a predetermined period of time, for example,10 minutes. The electric conductivity of the supernatant fluid at thattime may be measured using a conductance meter, “EC METER CM-30G”,manufactured by DKK-TOA CORPORATION or the like. There is no speciallimitation on the water used for the washing treatment and measurementof the electric conductivity, but desalted water or distilled water ispreferable. Among them, the one having low electric conductivity isparticularly preferable. Its electric conductivity should be usually0.0064 mS/m or higher, and usually 1 mS/m or lower, preferably 0.5 mS/mor lower. The measurement of the electric conductivity is usuallycarried out at a room temperature (around 25° C.).

Classification Step

Classification treatment can be done by, for example, levigation, orusing various classifiers such as air current classifier or vibratingsieve. Particularly, a dry classification using a nylon mesh can bepreferably used to obtain the phosphor of good dispersibility withweight-average median diameter of about 10 μm.

In addition, combination of a dry classification using nylon mesh andelutriation, treatment can obtain the phosphor of good dispersibilitywith weight-average median diameter of about 20 μm.

In a levigation or elutriation treatment, in order for phosphorparticles to be dispersed in an aqueous medium at a concentration ofaround 0.1 weight % to 10 weight % and also to prevent the degradationof the phosphor, the pH of the aqueous medium is set at usually 4 orlarger, preferably 5 or larger, and usually 9 or smaller, preferably 8or smaller. In addition, for achieving the phosphor with weight-averagemedian diameter such as described above by a levigation or elutriationtreatment, it is preferable to perform two-step sieving in which, forexample, particles of 50 μm or smaller are sifted out and then particlesof 30 μm or smaller are sifted out, in terms of balance between theoperating efficiency and the yield. Regarding the lower limit ofsieving, it is preferable to sift out particles of usually 1 μm orlarger, and preferably 5 μm or larger.

Surface Treatment Step

When the obtained phosphor of the present invention (I) is used tomanufacture a light emitting device, the surface of the phosphors may besubjected to surface treatment if necessary such as covering thesurfaces with some foreign compound, in order to improve weatherabilitysuch as moisture resistance or to improve dispersibility in a resin inthe phosphor-containing part of the light emitting device describedlater.

Examples of the substance that can be applied to the phosphor surface(hereinafter referred to as “surface treatment substance” asappropriate) include: organic compounds, inorganic compounds, and glassmaterials.

Examples of the organic compounds include: thermofusible polymer such asacrylic resin, polycarbonate, polyamide and polyethylene; latex; andpolyorganosiloxane.

Examples of the inorganic compounds include: metal oxides such asmagnesium oxide, aluminum oxide, silicon oxide, titanium oxide,zirconium oxide, tin oxide, germanium oxide, tantalum oxide, niobiumoxide, vanadium oxide, boron oxide, antimony oxide, zinc oxide, yttriumoxide and bismuth oxide; metal nitrides such as silicon nitride andaluminum nitride; orthophosphates such as calcium phosphate, bariumphosphate and strontium phosphate; polyphosphate; and combinations ofcalcium salt and phosphates of alkali metals and/or alkaline-earthmetals such as a combination of calcium nitrate and sodium phosphate.

Examples of the glass material include: boron silicate, phosphorussilicate, and alkali silicate.

These surface treatment substances can be used either as a single one oras a combination of two or more kinds in any combination and in anyratio.

The phosphor of the present invention (I) obtained by the surfacetreatment mentioned above has a surface treatment substance existing onits surface. The mode of existence of the surface treatment substancecan be as follows, for example.

(i) The above surface treatment substance constitutes a continuous layerand covers the surface of the phosphor.

(ii) The above surface treatment substance is attached to the surface ofthe phosphor as numerous microparticles and these microparticles coverthe surface of the phosphor.

There is no special limitation on the amount of the surface treatmentsubstance which can cover or be attached to the surface of the phosphor,insofar as the advantage of the present invention is not significantlyimpaired. However, the amount, relative to the weight of the phosphor,is usually 0.1 weight % or more, preferably 1 weight % or more, morepreferably 5 weight % or more, still more preferably 10 weight % ormore, and usually 50 weight % or less, preferably 30 weight % or less,more preferably 20 weight % or less. When the amount of the surfacetreatment substance relative to that of the phosphor is too large, theluminescent characteristics of the phosphor may be impaired. When it istoo small, the coverage of the surface may be insufficient, and moistureresistance and dispersibility may not be improved.

There is no special limitation on the film thickness (layer thickness)of the surface treatment substance formed by the surface treatment,insofar as the advantage of the present invention is not significantlyimpaired. However, it is usually 10 nm or larger, preferably 50 nm orlarger, and usually 2000 nm or smaller, preferably 1000 nm or smaller.When the layer is too thick, the luminescent characteristics of thephosphor may be impaired. When it is too thin, the coverage of thesurface may be insufficient, and moisture resistance and dispersibilitymay not be improved.

No particular limitation is imposed on the method of such surfacetreatment. The examples include the following coating treatment methodusing a metal oxide (silicon oxide).

The phosphor of the present invention (I) is added to an alcohol such asethanol, mixed and stirred. To this is added an alkaline aqueoussolution such as ammonia water, followed by stirring. A hydrolyzablesilicic acid alkyl ester such as tetraethyl orthosilicate is then addedand the mixture is stirred. The solution obtained is allowed to standfor 3 to 60 minutes, and then the supernatant containing silicon oxideparticles which remain unattached to the surface of the phosphor isremoved by pipetting or the like. Then, mixing in alcohol, stirring,allowing to stand and removal of the supernatant are repeated severaltimes and a drying is performed under a reduced pressure at 120° C. to150° C. for 10 minutes to 5 hours, for example 2 hours. Thereby, asurface-treated phosphor is obtained.

Examples of other surface treatment methods of phosphors include:various known methods such as a method in which spherical silicon oxidefine powder is attached to the phosphor (Japanese Patent Laid-OpenPublications No. Hei 2-209989 and No. Hei 2-233794), a method in which acoating film of Si-compound is attached to the phosphor (Japanese PatentLaid-Open Publication No. Hei 3-231987), a method in which the surfaceof the phosphor is covered with polymer microparticles (Japanese PatentLaid-Open Publication No. Hei 6-314593), a method in which the phosphoris coated with organic, inorganic, glass and the like materials(Japanese Patent Laid-Open Publication No. 2002-223008), a method inwhich the surface of the phosphor is covered by means of chemical vaporreaction (Japanese Patent Laid-Open Publication No. 2005-82788), and amethod in which particles of a metal compound is attached (JapanesePatent Laid-Open Publication No. 2006-28458).

[2-6. Production Method Using Alloy]

The phosphor of the present invention (I) can be produced by, inaddition to the above-mentioned production method using the above rawmaterials, a production method using alloy as material.

As refinement technologies of elemental metals that are widely utilizedindustrially, sublimation refining, floating zone refining, distillationmethod and the like are known. As such, there are many elemental metalsthat can be purified easier than compounds. Accordingly, a method inwhich elemental metals necessary for producing a phosphor are used asstarting materials for forming alloy and the phosphor is produced fromthe alloy is superior to the method using compounds as material, in thatmaterial of higher purity can be easily obtained. In addition, from theviewpoint of homogeneous dispersion of activator element within thecrystal lattice, elemental metal can be used advantageously asconstituent elements for the activator element. This is because bymelting the elemental metal to form alloy the activator element can beeasily dispersed uniformly.

From the above standpoint, by using, as raw material, alloy containingat least a part of the metal elements that constitute the desirablephosphor, preferably containing all the metal elements that constitutethe desirable phosphor, it is possible to produce a high-performancephosphor industrially. In what follows, explanation will be given on anexample of the production method (alloy method) using such alloy as rawmaterial.

In the alloy method, alloy that can be used as material for the phosphoris first prepared. To obtain the alloy, starting material such as asimple substance is usually melted. There is no limitation on themelting method and various known methods such as arc melting orhigh-frequency dielectric melting can be used.

As the material alloy, any ones can be used insofar as the phosphor ofthe present invention (I) can be obtained. The alloy can be used eitheras a single kind or as a mixture of two or more kinds in any combinationand in any ratio. It is particularly preferable to use an appropriatecombination of alloy phases that are present stably such as LaSi₂,Ce_(x)La_(1−x)Si₂ (where, 0<x<1), LaSi, La₃Si₂, La₅Si₃, Ca₂₄Si₆₀,Ca₂₈Si₆₀, CaSi₂, Ca₃₁Si₆₀, Ca₁₄Si₁₉, Ca₃Si₄, CaSi, Ca₅Si₃, and Ca₂Si.

Other examples of the alloy that can be used as the material are asfollows. Known examples of the alloy containing Si and alkaline-earthmetal include: Ca₇Si, Ca₂Si, Ca₅Si₃, CaSi, Ca₂Si₂, Ca₁₄Si₁₉, Ca₃Si₄,SrSi, SrSi₂, Sr₄Si₇, Sr₅Si₃, and Sr₇Si. Known examples of the alloycontaining Si, aluminum and alkaline-earth metal include:Ca(Si_(1−x)Al_(x))₂, Sr(Si_(1−x)Al_(x))₂, Ba(Si_(1−x)Al_(x))₂, andCa_(1−x)Sr_(x)(Si_(1−y)Al_(y))₂. Of these, A¹(B¹ _(0.5)Si_(0.5))₂(where, A¹=(Ca,Sr,Ba) and B¹=(Al,Ga)) has been studied regarding itssuperconductivity and reported in such references as Japanese PatentLaid-Open Publication (Kokai) No. 2005-54182, M. Imai, Applied PhysicsLetters, 80 (2002) 1019-1021, and M. Imai, Physical Review B, 68,(2003), 064512, or the like.

Alloy in the form of a lump can hardly react to be formed into phosphor,and therefore it is preferable to adjust its particle diameter to apredetermined level by performing a pulverization. The preferableparticle diameter is in the range of usually 1 μm or larger and 500 μmor smaller. Even if there is heterogeneity in the alloy, homogenizationwill be achieved by this pulverization process from a macroscopicviewpoint. However, it is not yet desirable that there is heterogeneityin its particle composition microscopically. Therefore, it is preferablethat the alloy is homogeneous as a whole.

The alloy powder thus obtained is usually filled into a vessel such as acrucible or a tray, and placed in a heating furnace in which control ofthe atmosphere is possible. Concerning the material of the vessel,sintered boron nitride is desirable because it has low reactivity withmetal compounds.

Subsequently, a gas containing nitrogen is passed until the atmosphereof the system is sufficiently replaced with the gas. If considerednecessary, the gas may be passed after the air is evacuated from thesystem first. For the case of production of an oxynitride, a mixed gasof nitrogen and oxygen can also be used.

Then, the phosphor of the present invention (I) can be prepared byfiring the alloy powder. At this point, it is desirable that theabove-mentioned alloy powder is fired with its volume filling ratemaintained at 40% or lower. The volume filling rate can be calculated bythe formula: (bulk density of the mixed powder)/(theoretical density ofthe mixed powder)×100[%].

Incidentally, nitride formation reaction of metals is usually anexothermic reaction. Accordingly, there is a possibility that the alloysmelt again due to reaction heat liberated suddenly and its surface areasdecrease, while producing phosphor by the alloy method. Such a reductionin the surface area may lead to a delay in reaction between the alloyand the nitrogen gas. Therefore, in an alloy method, it is preferable tomaintain a reaction rate that does not allow melting of the alloy forproducing a high-performance phosphor in a stable manner.

[3. Phosphor (II)]

[3-1. Crystal Phase of Phosphor (II)]

The present inventors made a search for nitrides and oxynitrides ofrare-earth elements and Si, for obtaining a new phosphor. As aconsequence, they have found a substance including a crystal phase witha composition range represented by the general formula [II] below.

Namely, the phosphor of the present invention (II) includes a crystalphase represented by the general formula [II] below.R_(3−x−y−z+w2)M_(z)A_(1.5x+y−w2)Si_(6−w1−w2)Al_(W1+w2)O_(y+w1)N_(11−y−w1)  [II](In the formula [II], R represents at least one kind of a rare-earthelement selected from the group consisting of La, Gd, Lu, Y and Sc. Mrepresents at least one kind of a metal element selected from the groupconsisting of Ce, Eu, Mn, Yb, Pr and Tb. A represents at least one kindof a bivalent metal element selected from the group consisting of Ba,Sr, Ca, Mg and Zn. And, x, y, z, w1 and w2 are the numeric values in thefollowing ranges:( 1/7)≦(3−x−y−z+w2)/6<(½),0≦(1.5x+y−w2)/6<(9/2),0≦x<3,0≦y<2,0<z<1,0≦w1≦5,0≦w2≦5, and0≦w1+w2≦5.)

In the following, explanation will be given on the crystal phaserepresented by the general formula [II] in more detail.

The points of the general formula [II] are the same as those alreadyexplained for the crystal phase of the general formula [I], except forthe points on the range of “x”, the range of (1.5x+y)/6, the examples ofthe chemical composition, and the space group and powder X-raydiffraction pattern of the crystal phase.

Namely, the R of the general formula [II] is in the same way asdescribed in the section of “• Regarding R” of the general formula [I].

The M of the general formula [II] is in the same way as described in thesection of “• Regarding M” of the general formula [I].

The A of the general formula [II] is in the same way as described in thesection of “• Regarding A” of the general formula [I].

The Si and Al of the general formula [II] are in the same way asdescribed in the section of “• Regarding Si and Al” of the generalformula [I].

The y of the general formula [II] is in the same way as described in thesection of “• Regarding range of y” of the general formula [I].

The z of the general formula [II] is in the same way as described in thesection of “• Regarding range of z” of the general formula [I].

The w1 and w2 of the general formula [II] are in the same way asdescribed in the section of “• Regarding range of w1 and w2” of thegeneral formula [I].

The (3−x−y−z+w2)/6 of the general formula [II] meets the same conditionas described in the section of “• Regarding conditions to be satisfiedby x, y and z” of the general formula [I].

The y+w1 of the general formula [II] meets the same condition asdescribed in the section of “• Regarding range of y+w1” of the generalformula [I].

The w1+w2 of the general formula [II] meets the same condition asdescribed in the section of “• Regarding range of w1+w2” of the generalformula [I].

In the general formula [II], 1.5x is a numerical value representing theamount of A substituted for a part of R by the above-mentioned R-Asubstitution. The numerical value of x in this case is 0 or larger,preferably 0.002 or larger, more preferably 0.01 or larger, still morepreferably 0.03 or larger, and smaller than 3, preferably 2.7 orsmaller, more preferably 2.5 or smaller, still more preferably 2.2 orsmaller. This is because a concentration quenching may occur, when thecontent of the activation element is too large.

In the general formula [II], the above-mentioned x, y and z satisfy thefollowing inequality.0≦(1.5x+y−w2)/6<(9/2)

Namely, in the general formula [II], “(1.5x+y−w2)/6” represents anumerical value of 0 or larger and smaller than 9/2. In addition, it ismore preferable that “(1.5x+y−w2)/6” is larger than 0, and at the sametime, x is larger than 0. The wavelength of emission peak can be therebyshifted to longer wavelength side. In this case, it is particularlypreferable that x in the general formula [II] is larger than 0 andsmaller than 3.

Preferable examples of the chemical composition of the above-mentionedgeneral formula [II] will be listed below. However, the crystal phasecomposition of the phosphor of the present invention (II) is not limitedto the following examples.

Preferable examples of the chemical composition of the general formula[II] with which oxygen is not mixed include:La_(1.37)Ce_(0.03)Ca_(2.40)Si₆N₁₁, La_(2.15)Ce_(0.10)Ca_(1.23)Si₆N₁₁,La_(2.57)Ce_(0.03)Ca_(0.60)Si₆N₁₁, La_(2.9)Ce_(0.1)Si₆N₁₁, andLa_(2.95)Ce_(0.05)Si₆N₁₁. Preferable examples in which oxygen is presentinclude: La_(1.71)Ce_(0.1)Ca_(1.57)Si₆O_(0.44)N_(10.56),La_(1.71)Ce_(0.03)Ca_(2.20)Si₆O_(1.00)N_(10.00),La_(2.37)Ce_(0.03)Ca_(0.75)Si₆O_(0.30)N_(10.70),La_(2.8)Ce_(0.1)Si₆N_(10.7)O_(0.3), andLa_(2.9)Ce_(0.1)Si_(5.9)N_(10.6)O_(0.4).

The crystal phase represented by the above-mentioned general formula[II] is essentially a new structure (with respect to its space group andsite constituent ratio) among alkaline-earth metal element—rare-earthmetal element (letting it “Ln”)—Si—N systems. In the following,explanation will be given on the difference between this crystal phaseand those of known substances.

The crystal phase represented by the above-mentioned general formula[II] is of P4bm or analogous space groups, whereas known SrYbSi₄N₇ andBaYbSi₄N₇ are of P6₃mc space group (refer to Non-Patent Document 2) andknown BaEu(Ba_(0.5)Eu_(0.5))YbSi₆N₁₁ is of P2₁3 space group (refer toNon-Patent Document 3). In this way, the space group of the crystalphase represented by the general formula [II] is significantly differentfrom those of previously known phosphors. In addition, the powder X-raydiffraction pattern of the crystal phase represented by the generalformula [II] is significantly different from those of previously knownphosphors. This apparently indicates that they have different crystalstructures from each other since crystal phases are judged on the basisof the powder X-ray diffraction patterns.

In addition, every point described in the section of “Other points ofcrystal phase of the general formula [I]” of the general formula [I] isalso true for the phosphor of the present invention (II).

[3-2. Characteristics of Phosphor (II)]

There is no limitation on the characteristics of the phosphor of thepresent invention (II) insofar as it comprises the crystal phaserepresented by the above-mentioned general formula [II]. However, itusually has such properties as described below.

[3-2-1. Characteristics on Luminescent Color of Phosphor (II)]

The phosphor of the present invention (II) usually emits yellow green toorange light. When the phosphor of the present invention (II) does notcomprise the A element (such as Ca or the like) in the above-mentionedgeneral formula [II], it usually emits yellow green to yellow light. Onthe other hand, when the phosphor of the present invention (II)comprises the A element (such as Ca or the like) in the above-mentionedgeneral formula [II], it usually emits yellow to orange (yellow red)light. In addition, the luminescent color varies depending also on theamount of Ce, an activation element.

The color coordinates (x, y) of the fluorescence of the phosphor of thepresent invention (II) is usually within the area surrounded by (0.320,0.400), (0.320, 0.570), (0.600, 0.570), and (0.600, 0.400). It ispreferably within the area surrounded by (0.380, 0.430), (0.380, 0.560),(0.580, 0.560), and (0.580, 0.430). Accordingly, the color coordinate xof the fluorescence of the phosphor of the present invention (II) isusually 0.320 or larger, preferably 0.380 or larger, and usually 0.600or smaller, preferably 0.580 or smaller. On the other hand, the colorcoordinate y is usually 0.400 or larger, preferably 0.430 or larger, andusually 0.570 or smaller, preferably 0.530 or smaller.

The color coordinate of fluorescence can be calculated from the emissionspectrum to be described later. In this context, the above-mentionedcolor coordinates (x, y) mean those in the CIE standard colorimetricsystem of the luminescent color when excited with light having 460-nmwavelength.

[3-2-2. Characteristics on Emission Spectrum]

There is no special limitation on the spectrum (emission spectrum) ofthe fluorescence emitted by the phosphor of the present invention (II).However, the wavelength of emission peak of the emission spectrum whenexcited with light of 460-nm wavelength is in the range of usually 480nm or longer, preferably 510 nm or longer, more preferably 530 nm orlonger, and usually 620 nm or shorter, preferably 600 nm or shorter,more preferably 580 nm or shorter.

The wavelength of emission peak of the present invention depends on thecomposition of the crystal phase contained. For example when thephosphor of the present invention (II) does not include the A element(such as Ca or the like) of the above-mentioned general formula [II] inits composition, the wavelength of emission peak of the emissionspectrum when excited with light of 460-nm wavelength is in the range ofusually 480 nm or longer, preferably 500 nm or longer, more preferably515 nm or longer, and usually 600 nm or shorter, preferably 580 nm orshorter, more preferably 575 nm or shorter.

In addition, the full width at half maximum (FWHM) of the emission peakof the phosphor of the present invention (II), when excited with lightof 460-nm wavelength, is usually 100 nm or longer, preferably 110 nm orlonger, more preferably 130 nm or longer. Such a large full width athalf maximum can enhance the color rendering of the light emittingdevice or the like which uses the phosphor of the present invention (II)and a blue LED or the like in combination. In addition, since thephosphor of the present invention (II) has a sufficient emissionintensity also at longer wavelength region (namely, around 630 nm to 690nm) than that of yellow light, a warm white light can be obtained whenincorporated with a blue LED. This characteristic of the phosphor of thepresent invention (II) is much superior to that of known YAG:Cephosphors (the FWHM of commercially available P46-Y3 is 126 nm). Thereis no special limitation on the upper limit to the full width at halfmaximum of the emission peak, but usually it is 280 nm or smaller.

In addition, the emission spectrum of the phosphor of the presentinvention (II) containing infinitesimal or less amount of alkaline-earthmetal, such as typified by that of x=0, usually exhibits a uniquewaveform satisfying the formula [B] below when excited with light of460-nm wavelength.I(B)/I(A)≦0.88  [B](In the above formula [B], I(A) represents the emission intensity of themaximum peak wavelength that is present in the wavelength range of 500nm or longer and 550 nm or shorter, and I(B) represents the emissionintensity of the wavelength that is longer than the maximum peakwavelength by 45 nm.)

Namely, in the phosphor of the present invention (II), theabove-mentioned I(B)/I(A) is usually 0.88 or smaller, preferably 0.87 orsmaller, and more preferably 0.85 or smaller. The I(B)/I(A) having sucha small value leads to an advantageous effect that the phosphor canfunction as a yellow green to green phosphor. There is no limitation onthe lower limit of the I(B)/I(A), but it is usually 0.5 or larger, andpreferably 0.7 or larger.

When Ca is not contained as the bivalent metal element A of the generalformula [II], the emission spectrum of the phosphor of the presentinvention (II) tends to be such a unique waveform. Accordingly, it canbe inferred that the emission spectrum can be controlled, in terms ofthe above-mentioned condition (formula) [B], by adjusting the content ofthe bivalent metal element A.

In this regard, the phosphor of the present invention (II) shows such aunique emission spectrum even without washing it with a strong acid suchas aqua regia. Conventional phosphors usually exhibit emission spectrathat are unique to the phosphors only when crystal phases other thanthose desired are removed by washing with a strong acid or the like. Incontrast, the phosphor of the present invention (II) shows a uniquecharacteristic of exhibiting such a unique emission spectrum evenwithout washing as described above. It can be inferred that this isbecause the phosphor is produced by a production method using alloy, asdescribed later.

The measurement of the emission spectrum of the phosphor of the presentinvention (II) and the calculation of its light emitting area,wavelength of emission peak, and full width at half maximum of the peakcan be carried out by, for example, using a fluorescence measurementapparatus manufactured by JASCO corporation at a room temperature(usually, 25° C.).

[3-2-3. Excitation Wavelength]

The phosphor of the present invention (II) can be excited by lightshaving a variety of wavelengths (excitation wavelengths) depending onthe composition or the like of the phosphor of the present invention(II). However, the excitation wavelength is usually the same as that forthe phosphor of the present invention (I).

[3-2-4. Weight-Average Median Diameter]

The weight-average median diameter of the phosphor of the presentinvention (II) is usually the same as that of the phosphor of thepresent invention (I).

[3-2-5. Chemical Resistance]

The phosphor of the present invention (II) is usually superior inchemical resistance as in the case with the phosphor of the presentinvention (I).

[3-2-6. Temperature Characteristics]

The temperature characteristics of the phosphor of the present invention(II) is usually the same as that of the phosphor of the presentinvention (I).

[3-2-7. Quantum Efficiency]

The quantum efficiencies such as external quantum efficiency, internalquantum efficiency, and absorption efficiency of the phosphor of thepresent invention (II) are usually the same as those of the phosphor ofthe present invention (I).

[3-2-8. Content of Impurity]

There are less amount of impurity phases in the phosphor of the presentinvention (II) even without performing washing or other specialprocedures after it is produced. Such a small amount of impurity phasescan be verified by the powder X-ray diffraction pattern.

The phosphor of the present invention (II) has a peak at 2θ from 17° to20°, in the powder X-ray diffraction pattern measured with CuKα line(1.54184 Å), and its peak intensity ratio I related to a peak present at2θ from 21° to 24° is usually 0.05 or smaller, preferably 0.04 orsmaller. Such a small amount of impurity phase can lead to a highemission intensity even when a washing step or the like is not carriedout. Incidentally, there is no limitation on the lower limit thereof.However, it is usually 0.001 or larger, even though the lower limit isideally 0.

The above-mentioned peak intensity ratio I is the ratio (I_(p))/I_(max)of the peak height I_(p), present at from 21° to 24°, to themost-intensive peak height I_(max), present at 2θ from 17° to 20°, inthe powder X-ray diffraction pattern at 2θ from 10° to 60°. In thiscontest, the values of the peak intensities are used after backgroundcorrection.

[3-3. Advantageous Effects of Phosphor of Present Invention (II)]

As described above, the phosphor of the present invention (II) containsmuch red light component and can emit lights having large full width athalf maximums. Namely, the emission intensity of the phosphor of thepresent invention (II) is sufficient at red, longer wavelength region,and the emission spectrum thereof shows an emission peak withsignificantly large full width at half maximum. Accordingly, when thephosphor of the present invention (II) is used for a white lightemitting device, the white light emitting device can emit warm whitelight with high color rendering.

In addition, the phosphor of the present invention (II) can be excitedparticularly efficiently by a near-ultraviolet or blue semiconductorluminous element and emit yellow green to orange fluorescence, usually.

Furthermore, in the phosphor of the present invention (II), there isusually less reduction in emission efficiency associated withtemperature rising than YAG:Ce phosphors, which have been frequentlyused for white light emitting devices conventionally.

[3-4. Use of Phosphor of Present Invention (II)]

There is no limitation on the use of the phosphor of the presentinvention (II). However, it can be used, for example, in the same way asthe phosphor of the present invention (I), making use of theabove-mentioned advantageous effects. However, since the phosphor of thepresent invention (II) is usually a yellow green to orange phosphor,preferable examples of the above-mentioned other phosphor to be combinedwith the phosphor of the present invention (II) include: phosphorsemitting blue, blue green, green, yellow green, yellow, orange, red, ordeep red light. It is particularly preferable to use a blue lightemitting diode, as excitation light source, and a green or red phosphorin combination with the phosphor of the present invention (II), becauseit can realize a white light emitting device. Moreover, a desirablewhite light emitting device can be realized also by using anear-ultraviolet light emitting diode and a blue phosphor, a greenphosphor, and a red phosphor in combination with the phosphor of thepresent invention (II). By adding a deep red phosphor to these whitelight emitting devices, the color rendering thereof can be furtherenhanced.

[4. Production Method of Phosphor (II)]

The production method of the phosphor of the present invention (II)uses, as at least a part of the raw material, an alloy (hereinafterreferred to as “alloy for phosphor precursor” as appropriate) containingtwo or more kinds of the metal elements that are included in the crystalphase represented by the general formula [II]. The phosphor of thepresent invention (II) is produced usually by mixing other materials ifnecessary to the above-mentioned alloy and subjecting the mixture to anitriding treatment (hereinafter referred to as “secondary nitridingprocess” as appropriate) in which the mixture is fired under anitrogen-containing atmosphere.

As refinement technologies of elemental metals that are widely utilizedindustrially, sublimation refining, floating zone refining, distillationmethod and the like are known. As such, there are many elemental metalsthat can be purified easier than compounds. Accordingly, a method inwhich elemental metals necessary for producing a phosphor are used asstarting materials for forming an alloy and the phosphor is producedfrom the obtained alloy for phosphor precursor is superior to the methodusing metal compounds as raw materials, in that a material of higherpurity can be easily obtained. In addition, an elemental metal can beused advantageously for constituting the activator element, from theviewpoint of homogeneous dispersion of the activator element within thecrystal lattice. This is because by melting the elemental metal to forman alloy the activator element can be easily dispersed uniformly.

From the above standpoint, it is possible to produce a high-performancephosphor industrially by using, as raw material, an alloy for phosphorprecursor containing at least a part of or preferably all of the metalelements that constitute the desirable phosphor, and nitriding thealloy.

In the following, such a production method (hereinafter referred to as“the production method (II) according to the present invention” asappropriate) will be described as an example of the production method ofthe phosphor of the present invention (II).

[4-1. Preparation of Alloy for Phosphor Precursor]

In the production method (II) according to the present invention, analloy for phosphor precursor, which can be used as the material for thephosphor (II), is first prepared. To obtain the alloy for phosphorprecursor, starting materials (hereinafter referred to as “materialmetals” as appropriate) such as elemental metals or metal alloys areusually melted. There is no limitation on the melting method and variousknown methods such as arc melting or high-frequency dielectric meltingcan be used.

[4-1-1. Weighing of Material Metal]

As material metal can be used materials such as metal or alloy of thecorresponding metal. Further, material metal corresponding to theelements contained in the phosphor of the present invention (II) can beused either as a single one or as a mixture of two or more kinds in anycombination and in any ratio. However, as material metal of the metalelement M which is the activating element (for example, material metalcorresponding to Eu or Ce) can be preferably used Eu metal or Ce metal,because these materials can be obtained easily.

It is preferable that the purity of metal used as the material metal ofthe alloy for phosphor precursor is high. Specifically, from thestandpoint of luminescent characteristics of the synthesized phosphor,it is preferable to use a metal the content of impurities of which is0.1 mole percent or less, more preferably 0.01 mole percent or less asthe material metal corresponding to the activating element M. Further,regarding metals used as material metals of elements other than theactivating element M, the content of impurities is preferably 0.1 molepercent or less, more preferably 0.01 mole percent or less for the samereason as described above for the activating element M. For example,when the impurity is at least one element selected from the groupconsisting of Fe, Ni and Co, the content of each impurity is usually 500ppm or less, preferably 100 ppm or less.

There is no special limitation on the form of the material metals.Usually, grains or lumps with a diameter from several mm to several tensmm are used. In this context, those of a diameter of 10 mm or larger arecalled lumps and those of a diameter of less than 10 mm are calledgrains.

There is no special limitation on the form, such as grains or lumps, ofthe material metal corresponding to the alkaline-earth metal elements.It is preferable to select a suitable form depending on the chemicalproperties of the corresponding material metal. For example, Ca isstable in air in the form of both grains and lumps and therefore bothforms can be used. Sr is chemically reactive and it is preferable to useit in the form of lumps.

For metal elements that are liable to be lost at the time of melting dueto vaporization or reaction with crucible material, prior weighing of anexcess amount may be useful if considered appropriate.

[4-1-2. Melting of Material Metal]

After weighing material metals, the corresponding material metals aremelted to an alloy to produce the alloy for phosphor precursor (meltingprocess). The alloy for phosphor precursor obtained contains two or morekinds of metal elements constituting the phosphor of the presentinvention (II). Even when one alloy for phosphor precursor does notcontain all of the metal elements constituting the phosphor of thepresent invention (II), it is possible to produce the phosphor of thepresent invention (II) by combining two or more kinds of alloys forphosphor precursor and/or other material (such as metals) in the primaryor secondary nitriding process to be described later.

There is no special limitation on the method of melting the materialmetals and any method can be used. For example, such methods asresistance heating method, electron beam method, arc melting method andhigh-frequency dielectric heating method (hereinafter also referred toas “high-frequency dielectric melting method”) can be used. It is alsopossible to combine any two or more of these methods for melting.

Examples of the material of crucible that can be used at the time ofmelting include: alumina, calcia, graphite, and molybdenum.

When an alloy for phosphor precursor containing metal elements which cannot be melted simultaneously, such as Si and alkaline-earth metal, isproduced, production can be effected by mixing other metal materialafter producing a mother alloy. For the details of the method in such acase, reference can be made to the pamphlet of International PublicationNo. WO 2006/106948.

Specific temperature condition and melting time at the time of meltingof the material metals can be set appropriately depending on eachmaterial metal used, for any material metal used.

There is no special limitation on the atmosphere at the time of meltingof the material metals, insofar as the alloy for phosphor precursor canbe obtained. Preferable is an inert gas atmosphere, in particular argonatmosphere. The inert gas can be used either as a single one or as amixture of two or more kinds in any combination and in any ratio.

There is no special limitation on the pressure at the time of melting ofthe material metals, insofar as the alloy for phosphor precursor can beobtained. A pressure of 1×10³ Pa or higher is preferable, and a pressureof 1×10⁵ Pa or lower is preferable. From the standpoint of safety, it ispreferable to select the atmospheric pressure or lower pressure.

[4-1-3. Casting of Molten Metal]

An alloy for phosphor precursor can be obtained by melting the materialmetals described above. This alloy for phosphor precursor is usuallyobtained as molten metal of the alloy. However, there are a number oftechnical difficulties in the direct production of the phosphor (II)from this molten metal of the alloy. Therefore, it is preferable toobtain a coagulated matter (hereinafter referred to as “alloy ingot” asappropriate) through a casting process in which this molten metal of thealloy is poured into a metallic mold and molded.

However, in this casting process, segregation is likely to occurdepending on cooling speed of the molten metal, and a bias is likely tobe caused in the composition of the alloy for phosphor precursor, whichwas homogeneous in the molten state. Therefore, it is preferable thatthe cooling speed is as rapid as possible. Further, it is preferable touse as a metallic mold a material with good thermal conductivity such ascopper, and to select a form in which dissipation of heat is easy. It isalso preferable to devise such means as cooling with water to cool themetallic mold if necessary.

It is preferable, through the attempts mentioned above, to induce rapidcoagulation after the molten metal is poured into the metallic mold, forexample by using a metallic mold which has a large area of base relativeto its thickness.

The degree of segregation is different depending on the composition ofthe alloy for phosphor precursor, and therefore, it is preferable toobtain samples from several locations of the coagulated matter, toanalyze the composition by means of, for example, ICP emissionspectroscopy, and to determine the cooling speed necessary forprevention of the segregation.

As atmosphere at the time of casting, preferable is an inert gasatmosphere, particularly argon atmosphere. The inert gas can be usedeither as a single one or as a mixture of two or more kinds in anycombination and in any ratio.

[4-1-4. Milling of Alloy Ingot]

It is preferable to make the alloy for phosphor precursor a powder ofdesired particle diameter before a heating process. Therefore, it ispreferable to subject the alloy ingot (pulverizing process), obtained inthe casting process, to a subsequent milling (milling process) so as toobtain an alloy powder of desired particle diameter and desired particlesize distribution to be used as material of the phosphor.

There is no special limitation on the method of milling. For example,dry method and also wet method using an organic solvent such as ethyleneglycol, hexane or acetone can be used.

The dry method will be explained in detail below as an example.

This milling process can be divided into plural number of processes, asneeded, such as coarse milling process, medium milling process, and finemilling process. The same milling instrument can be used throughoutthese processes or different ones can be used in different processes.

Coarse milling process is a process in which about 90 weight % of alloypowder is milled to particles of 1-cm particle diameter or smaller. Themilling instruments which can be used include a jaw crusher, gyratorycrusher, crushing roll and impact crusher. Medium milling process is aprocess in which about 90 weight % of alloy powder is milled toparticles of 1-mm particle diameter or smaller. The milling instrumentswhich can be used include a corn crusher, crushing roll, hammer mill anddisc mill. Fine milling is a process in which alloy powder is milled toparticles of the weight-average median diameter to be described later.The milling instruments which can be used include a ball mill, tubemill, rod mill, roller mill, stamp mill, edge runner, vibration mill andjet mill.

Among others, it is preferable to use a jet mill in the final millingprocess from the standpoint of preventing mixing of impurities. When ajet mill is used, it is preferable to mill preliminarily the alloy ingotto a level of 2-mm particle diameter or smaller. In using a jet mill,milling is effected by making use of expansion energy of fluid ejectedfrom nozzle pressure to atmospheric pressure, and it is possible tocontrol particle diameter by adjusting milling pressure and to preventmixing of impurities. Although the milling pressure depends on theinstrument used, the gauge pressure is usually 0.01 MPa or higher,preferably 0.05 MPa or higher, more preferably 0.1 MPa or higher, andusually 2 MPa or lower, preferably 0.4 MPa or lower, more preferably 0.3MPa or lower. When the gauge pressure is too low, the particle diameterof the obtained particles is possibly too large. When it is too high,the particle diameter of the obtained particles is possibly too small.

In all the cases, it is preferable, in order to prevent contaminationdue to impurities such as iron during the milling process, to give dueconsideration to the compatibility between the material of the millinginstrument and the material to be milled. For example, ceramic lining ispreferable at the area where contact with powder is possible. Ofceramics, preferable examples include: alumina, silicon nitride,tungsten carbide and zirconia. These substances can be used either as asingle one or as a combination of two or more kinds in any combinationand in any ratio.

Further, in order to prevent oxidation of the alloy powder, it ispreferable to perform the milling process in an atmosphere of inert gas.There is no special limitation on the kind of inert gas used. Usually,of the gases such as nitrogen, argon and helium, one gas can be usedsingly or a mixture of two or more gases can be used. In particular,nitrogen is preferable from the standpoint of cost efficiency.

There is no special limitation on the concentration of oxygen in theatmosphere, insofar as oxidation of the alloy powder can be prevented.Usually, it is 10 volume % or lower, preferably 5 volume % or lower. Thelower limit of oxygen concentration is usually about 10 ppm. By adoptingspecific oxygen concentration range, oxidation film is probably formedon the surface of the alloy during the milling and stabilization ensues.When milling is carried out in an atmosphere in which oxygenconcentration is 5 volume % or higher, it is likely that explosion ofpowder dust occurs during milling. Therefore, it is desirable to installa mechanism for preventing occurrence of powder dust.

In order to prevent rise in temperature of the alloy powder during themilling process, cooling may be provided when considered necessary.

[4-1-5. Classification of Alloy Powder]

It is preferable to use the alloy powder obtained in the above processafter it is adjusted in size to the desired weight-average mediandiameter D₅₀ with desired particle size distribution (classificationprocess) by means of, for example, sieving instrument utilizing meshsuch as vibrating screen and sifter, inertial classification instrumentsuch as air separator, and centrifuge such as cyclone. The subsequentprocedures will then be easy.

In the adjustment of the particle size distribution, it is preferable toclassify coarse particles and recycle them in the milling instrument,and to make classification and/or recycle a continuous process.

In this classification process also, it is preferable to perform it inan atmosphere of inert gas. There is no special limitation on the kindof inert gas used. Usually, of the gases such as nitrogen, argon andhelium, one gas can be used singly or a mixture of two or more gases canbe used. In particular, nitrogen is preferable from the standpoint ofcost efficiency. The concentration of oxygen in the atmosphere of inertgas is preferably 10 volume % or lower, particularly 5 volume % orlower.

Particle diameter to be adjusted by the classification described abovediffers depending on the activity of the metal elements constituting thealloy powder. Its weight-average median diameter D₅₀ is usually 100 μmor smaller, preferably 80 μm or smaller, more preferably 60 μm orsmaller, and usually 0.1 μm or larger, preferably 0.5 μm or larger, morepreferably 1 μm or larger. When the alloy for phosphor precursorcontains Sr, which is highly reactive with atmospheric gases, theweight-average median diameter D₅₀ of the alloy powder is usually 5 μmor larger, preferably 8 μm or larger, more preferably 10 μm or larger,particularly preferably 13 μm or larger. When the particle diameter ofthe alloy powder is smaller than the aforementioned range ofweight-average median diameter D₅₀, the rate of heat liberation at thetime of reaction such as nitriding tends to be high, leading todifficulty in controlling the reaction. Also, the alloy powder is thenliable to be oxidized in air and the phosphor obtained may take upoxygen readily, leading to difficulty in handling. On the other hand,when the particle diameter of the alloy powder exceeds theweight-average median diameter D₅₀ mentioned above, reaction such asnitriding inside the alloy particles may not be sufficient.

[4-1-6. Production of Alloy by Atomizing Method or the Like]

On the other hand, the alloy for phosphor precursor can also be producedthrough processes (a) to (c) described below, in addition to the methoddescribed above. In this way, it is possible to obtain an alloy powderto be used as material of the phosphor whose angle of repose is 45degrees or less.

(a) Two or more kinds of material metals corresponding to metalsconstituting the phosphor (II) are melted, and the molten metal of thealloy containing these elements is prepared (melting process).

(b) The molten metal of the alloy is pulverized finely in an atmosphereof an inert gas (fine pulverizating process).

(c) The finely pulverized molten metal of the alloy is allowed tocoagulate to obtain an alloy powder (coagulation process).

In other words, in this method, molten metal of the alloy is pulverizedfinely in a gas and allowed to coagulate to obtain a powder. In the finemilling process (b) and coagulation process (c) described above, it ispreferable to prepare the powder by such methods as spraying moltenmetal of the alloy, fine milling into the shape of ribbons by rapidcooling through a roll or gas stream, or atomizing. Of these methods,atomizing is particularly preferable.

More specifically, reference can be made to known methods described inthe pamphlet of International Publication No. WO2007/135975, modifiedappropriately.

[4-2. Firing Process]

The alloy for phosphor precursor obtained as above (it may be in thepowder form or ingot form, preferably in the form of alloy powderdescribed earlier) is fired in an atmosphere containing nitrogen,resulting in nitridation. Thereby, the phosphor of the present invention(II) is obtained. In this firing process, the secondary nitridingprocess (namely, nitriding treatment step) described later is essential,and the primary nitriding process described below is performed whenneeded.

[4-2-1. Mixing of Material]

When the composition of the metal elements contained in the alloy forphosphor precursor is the same as the composition of the metal elementscontained in the crystal phase represented by the general formula [II],the alloy for phosphor precursor alone needs to be fired. When thecompositions are different, an alloy for phosphor precursor having adifferent composition, elemental metal, or metal compound can be mixedwith the alloy for phosphor precursor so that the composition of themetal elements contained in the material coincides with the compositionof the metal elements contained in the crystal phase represented by thegeneral formula [II]. Firing is then performed.

Even when the composition of the metal elements contained in the alloyfor phosphor precursor is the same as the composition of the metalelements contained in the crystal phase represented by the generalformula [II], by adding a nitride or oxynitride (it may be a nitride oroxynitride containing activating element, or may be the phosphor of thepresent invention (II) itself) to the alloy for phosphor precursor, heatreleasing speed per unit volume at the time of nitriding is suppressedand nitriding reaction proceeds smoothly, as described in the pamphletof International Publication No. WO2007/135975. The phosphor withexcellent characteristics can then be obtained with a high yield. Inproducing the phosphor of the present invention (II), the secondarynitriding process, described later, may be performed in the presence ofa suitable nitride or oxynitride by referring to the pamphlet ofInternational Publication No. WO2007/135975, which can be modifiedappropriately.

It is preferable that stably-existing alloy phases are used in anappropriate combination as alloys for phosphor precursor that can beused for the production of the phosphor of the present invention (II).Examples of such alloy phases include: LaSi₂, Ce_(x)La_(1−x)Si₂ (0<x<1),LaSi, La₃Si₂, La₅Si₃, Ca₂₄Si₆₀, Ca₂₈Si₆₀, CaSi₂, Ca₃₁Si₆₀, C₁₄Si₁₉,Ca₃Si₄, CaSi, Ca₅Si₃, Ca₂Si, Ca_(x)La_(3−x)Si₆ (0<x<3) andCe_(y)Ca_(x)La_(3−x−y)Si₆ (0<x<3, 0<y<3).

Other examples of the alloy for phosphor precursor include, as examplesof alloys containing Si and alkaline-earth metal, Ca₇Si, Ca₂Si, Ca₅Si₃,CaSi, Ca₂Si₂, Ca₁₄Si₁₉, Ca₃Si₄, SrSi, SrSi₂, Sr₄Si₇, Sr₅Si₃ and Sr₇Si.Further, examples of alloys containing Si, aluminum and alkaline-earthmetal include: Ca(Si_(1−x)Al_(x))₂, Sr(Si_(1−x)Al_(x))₂,Ba(Si_(1−x)Al_(x))₂ and Ca_(1−x)Sr_(x)(Si_(1−y)Al_(y))₂. Of these, A¹(B¹_(0.5)Si_(0.5))₂ (where, A¹=Ca,Sr,Ba, B¹=Al,Ga) has been investigatedregarding its superconductivity in such documents as Japanese PatentLaid-Open Publication (Kokai) No. 2005-54182, M. Imai “Applied PhysicsLetters” 80(2002)1019-1021, and M. Imai “Physical Review B” 68, (2003),064512.

There is no special limitation on the metal compound that can be mixedwith the alloy for phosphor precursor. Examples thereof include nitride,oxide, hydroxide, carbonate, nitrate, sulfate, oxalate, carboxylate, andhalide. Of these metal compounds, a suitable one can be selected, inlight of reactivity with the target compound or the level of NO_(x) orSo_(x) generated at the time of firing. It is preferable to use anitride and/or an oxynitride, as the phosphor of the present invention(II) is a nitrogen-containing phosphor. Nitrides are particularlypreferable, as they also work as a source of nitrogen.

Examples of the nitride and oxynitride include: nitrides of elementsconstituting the phosphor such as AlN, Si₃N₄, Ca₃N₂, Sr₃N₂ and EuN; andcomplex nitrides of elements constituting the phosphor such as CaAlSiN₃,(Sr,Ca)AlSiN₃, (Sr,Ca)₂Si₅N₈, CaSiN₂, SrSiN₂ and BaSi₄N₇.

The nitrides described above may contain a minute amount of oxygen.There is no special limitation on the ratio (molar ratio) ofoxygen/(oxygen+nitrogen) in the nitride, insofar as the phosphor of thepresent invention (II) can be produced. Usually, the ratio is 5% orsmaller, preferably 1% or smaller, more preferably 0.5% or smaller,still more preferably 0.3% or smaller, particularly preferably 0.2% orsmaller. When the ratio of oxygen in the nitride is too high, thebrightness may decrease.

There is no special limitation on the weight-average median diameter D₅₀of the metal compounds, insofar as no difficulty is encountered inmixing with other materials. However, it is preferably easy to be mixedwith other materials. For example, the weight-average median diameterD₅₀ similar to that of the alloy powder is desirable. No particularlimitation is imposed on the concrete value of weight-average mediandiameter D₅₀ of the metal compounds, insofar as the phosphor can beproduced. Usually, it is 200 μm or smaller, preferably 100 μm orsmaller, more preferably 80 μm or smaller, and still more preferably 60μm or smaller. It is preferably 0.1 μm or larger and more preferably 0.5μm or larger.

The above-mentioned alloy for phosphor precursor, metal element, andmetal compound can be used either as a single one or as a mixture of twoor more kinds in any combination and in any ratio, respectively.

There is no special limitation on the timing of mixing, insofar as it isbefore the secondary nitriding process. It may be before, during orafter the primary nitriding process described later. Or the mixing canbe done at 1 or 2 or more timings of these. However, when the primarynitriding process is performed, usually, the mixing is done after theprimary nitriding process and before the secondary nitriding process.

In producing a phosphor containing Ca, for example, an alloy containingall of the metal elements constituting the phosphor is unstable and itis difficult to obtain a monophasic phosphor. It is preferable to mix analloy for phosphor precursor containing a part of metal elementsconstituting the phosphor and one or more metal compounds containingother metal element(s) (for example, metal nitride(s)), therebypreparing a mixture containing all of the constituting elements as awhole. The mixture is then fired to produce the phosphor. The procedureat the time of production is then simple and emission efficiency of thephosphor can be improved.

When a phosphor not containing Ca is produced, it is preferable toprepare an alloy for phosphor precursor so that it contains all of themetal elements constituting the phosphor and fire it to produce thephosphor, for example. In this way, it is possible to readily produce anexcellent phosphor with a few processes. In previous production methodsnot using an alloy, the composition of metal elements contained in thematerial may vary during firing, and it was sometimes difficult toobtain a phosphor with a desired element composition ratio. By makinguse of an alloy for phosphor precursor, it is now possible to obtain aphosphor with a desired composition ratio simply by charging metalelements in stoichiometric amount calculated from the target phosphor.

[4-2-2. Primary Nitriding Process]

From the standpoint of producing the phosphor of the present invention(II) industrially efficiently, the primary nitriding process may beincluded before the secondary nitriding process, if consideredappropriate. This primary nitriding process is a process during whichthe alloy for phosphor precursor is preliminarily nitrided.Specifically, this preliminary nitriding is performed by heating thealloy for phosphor precursor at a predetermined temperature range for apredetermined length of time in a nitrogen-containing atmosphere. Byintroducing this primary nitriding process, it is possible to controlthe reactivity between the alloy and nitrogen in the secondary nitridingprocess and to produce the a phosphor from the alloy industrially.

In the explanation below, an alloy for phosphor precursor after theprimary nitriding process may be referred to as “nitrogen-containingalloy”.

Regarding this primary nitriding process, reference can be made to thepamphlet of International Publication No. WO2007/135975 pamphlet.Modification can be added thereto when considered appropriate.

[4-2-3. Cooling and Milling Process]

When the primary nitriding process is performed, after completion of theprimary nitriding process and before starting the secondary nitridingprocess, nitrogen-containing alloy obtained in the primary nitridingprocess may be cooled temporarily (cooling process). Regarding thiscooling process, reference can be made to the pamphlet of InternationalPublication No. WO2007/135975 pamphlet. Modification can be addedthereto when considered appropriate.

After cooling, milling and/or stirring is performed as appropriate. Theweight-average median diameter D₅₀ of the nitrogen-containing alloyafter milling is usually 100 μm or smaller, and is preferably similar tothat of the alloy powder before the primary nitriding process.

[4-2-4. Secondary Nitriding Process (Nitriding Treatment Step)]

In the secondary nitriding process, the phosphor of the presentinvention (II) is obtained through nitriding process of an alloy forphosphor precursor. As alloy for phosphor precursor can be employedeither an alloy for phosphor precursor without undergoing the primarynitriding process (preferably, its alloy powder) or an alloy forphosphor precursor which has undergone the primary nitriding process(namely, nitrogen-containing alloy, preferably its alloy powder). Bothcan also be combined. If considered necessary, material other than thealloy for phosphor precursor (for example, metal itself or metalcompound) can also be mixed. In the description below, the alloy forphosphor precursor (including nitrogen-containing alloy) and theabove-mentioned other material which serve as materials of the phosphorof the present invention (II) are collectively called “phosphormaterial” as appropriate.

Nitriding treatment at the time of the secondary nitriding process isperformed by heating phosphor material, filled in a firing vessel suchas a crucible or tray, in a nitrogen-containing atmosphere. A specificprocedure is as follows.

First, the phosphor material is filled into a firing vessel. Examples ofmaterial used for the firing vessel include boron nitride, siliconnitride, carbon, aluminum nitride and tungsten. Of these, boron nitrideis preferable for its corrosion-resistant characteristics. Theabove-mentioned material can be used either as a single one or as amixture of two or more kinds in any combination and in any ratio.

There is no special limitation on the shape of the firing vessel used.For example, its bottom may be circular or oval with no angles, or maybe of polygonal shape such as triangular or quadrangular. No particularlimitation is imposed on the height of the firing vessel, either,insofar as it can be accommodated in a heating furnace. It can be highor low. It is preferable to select a shape which permits efficient heatliberation.

This firing vessel filled with phosphor material is placed in a firinginstrument (also referred to as “heating furnace”). There is no speciallimitation on the firing instrument, insofar as the advantageous effectof the present invention is not impaired. However, it is preferable touse an instrument which permits easy control of an atmosphere in theinstrument and easy control of pressure. For example, a hot isostaticpressing instrument (HIP) or resistance-heating, vacuum,pressurized-atmosphere heat-treating furnace is desirable.

It is also preferable that a gas containing nitrogen is allowed to passthrough the firing instrument before initiation of heating to replace agas in the system sufficiently with the nitrogen-containing gas. Whenconsidered appropriate, vacuum is induced in the system beforeintroduction of the nitrogen-containing gas.

Examples of the nitrogen-containing gas used at the time of nitridinginclude gases containing nitrogen element such as nitrogen, ammonia or amixed gas of nitrogen and hydrogen. The nitrogen-containing gas can beused either as a single one or as a mixture of two or more kinds in anycombination and in any ratio. The concentration of oxygen in the systemaffects the oxygen content of the phosphor to be produced and too high acontent does not lead to high luminescence. Therefore, oxygenconcentration in the nitriding atmosphere should be as low as possible.It is usually 0.1 volume % or lower, preferably 100 ppm or lower, morepreferably 10 ppm or lower, and still more preferably 5 ppm or lower.Oxygen getter such as carbon or molybdenum may be included in theheating part of the system, as appropriate, to decrease theconcentration of oxygen. The oxygen getter can be used either as asingle one or as a mixture of two or more kinds in any combination andin any ratio.

Nitriding treatment is done by heating the phosphor material under theconditions where nitrogen-containing gas is filled in the system or itis passed through the system. The pressure at that time may be a littlelower than atmospheric pressure, equal to, or higher than atmosphericpressure. It is preferable, however, to maintain it higher thanatmospheric pressure in order to prevent mixing of atmospheric oxygen.When the pressure is lower than atmospheric pressure, it is possiblethat a large amount of oxygen mixes in the case of incompleteairtightness of the heating furnace, leading to deterioration ofluminous characteristics of the phosphor. The gauge pressure of thenitrogen-containing gas is preferably 0.2 MPa or higher, more preferably0.5 MPa or higher, and still more preferably 0.92 MPa or higher. Heatingat a high pressure of 20 MPa or higher is also possible. It ispreferably 200 MPa or lower.

There is no special limitation on the heating temperature of thephosphor material, insofar as the phosphor of the present invention (II)can be produced. Usually, it is 800° C. or higher, preferably 1000° C.or higher, more preferably 1200° C. or higher, and usually 2200° C. orlower, preferably 2100° C. or lower, more preferably 2000° C. or lower.When the heating temperature is lower than 800° C., time required fornitriding may be too long. On the other hand, when the heatingtemperature is higher than 2200° C., the nitride compound produced mayvolatilize or decompose, and chemical composition of the resultantnitride phosphor may be distorted, leading to deterioration of thephosphor characteristics and reproducibility of the process.

Further, the heating temperature differs depending on, for example, thecomposition of the alloy for phosphor precursor. It is preferable thatthe heating temperature is higher than the melting point of the alloyfor phosphor precursor usually by 300° C. or higher, preferably 400° C.or higher, more preferably 500° C. or higher, still more preferably 700°C. or higher. The melting point of the alloy can be determined bythermogravimetry-differential thermal analysis and usually 1000° C. orhigher and 1400° C. or lower, although it is different depending on thecomposition of the alloy. The temperature described above means thetemperature in the furnace at the time of heat treatment, namely presettemperature of the firing instrument.

In order to secure sufficient nitriding, it is preferable to slow downthe rate of temperature elevation in a temperature range around themelting point of the alloy for phosphor precursor, preferably in atemperature range lower than the above melting point by 150° C. orhigher than that temperature, or higher than the above melting point by100° C. or lower than that temperature (for example, temperature rangeof 800° C. to 1600° C.)

In the temperature range where speed of temperature elevation iscontrolled, the rate of temperature elevation is usually 5° C./min orless, preferably 3° C./min or less. When the temperature elevation rateis higher than the above range, it is difficult to avoid a rapidaccumulation of reaction heat and production of a phosphor with highbrightness tends to be difficult. There is no lower limit to the rate oftemperature elevation. From the standpoint of productivity, it isusually, 0.2° C./min or more, preferably 0.5° C./min or more.

Heating time at the time of nitriding treatment (length of time themaximum temperature is maintained) may be a period of time necessary forthe reaction between the phosphor material and nitrogen. Usually, it is1 min or longer, preferably 10 min or longer, more preferably 30 min orlonger, still more preferably 60 min or longer. When the heating time isshorter than 1 min, nitriding reaction may not be completed and aphosphor with excellent characteristics may not be obtained. The upperlimit of the heating time will be determined from consideration ofproduction efficiency, and usually, it is 24 hours or shorter.

Further, the secondary nitriding process may be repeated as pluralprocesses, as appropriate. In this case, the conditions at the time offirst firing (primary firing) and conditions at the time of second andlater firing (secondary firing) are as described above. The conditionsat the time of secondary and later firing may be the same as those ofthe primary firing or the conditions may be different.

Thus, by nitriding treatment of the phosphor material, it is possible toobtain the phosphor of the present invention (II) based on nitride oroxynitride.

In the secondary nitriding process, when the nitriding treatment of alarge amount of phosphor material is allowed to proceed all at once,nitriding reaction may proceed too rapidly depending on some conditions,leading possibly to deterioration of characteristics of the phosphor ofthe present invention (II). Therefore, when a large amount of phosphormaterial is subjected to heat treatment all at once, the condition ofraising temperature can be adjusted and thus, rapid progress ofnitriding reaction can be avoided, which is desirable. In such a case,reference can be made to the pamphlet of International Publication No.WO2007/135975 pamphlet. Modification can be added thereto whenconsidered appropriate.

As described above, it is possible to produce a phosphor of the presentinvention (II) by nitriding of an alloy for phosphor precursor (it maybe a nitrogen-containing alloy).

[4-2-5. Points to be Noted in the Secondary Nitriding Process (NitridingTreatment Step)]

As described above, nitriding reaction is an exothermic reaction. When alarge amount of phosphor material is nitrided by heating all at once atthe time of the secondary nitriding process (namely, nitriding treatmentstep), excessive exothermic reaction is liable to occur, leading toevaporation of a part of elements constituting the phosphor material orthermal fusion of particles of the alloy for phosphor precursor. Thismay result in deterioration of luminescent characteristics of thephosphor obtained, or the phosphor can not be obtained at all. It isthen preferable to adjust the temperature range of the secondarynitriding reaction, by referring to known method described in thepamphlet of International Publication No. WO2007/135975 and by modifyingthe method appropriately. Then it may be possible to suppress a suddenand rapid progress of the nitriding reaction even when the amount ofphosphor material to be treated is increased. It is then possible toproduce industrially a phosphor with excellent characteristics.

[4-2-6. Flux]

In the secondary nitriding process, flux may be added to the reactionsystem in order to secure growth of good quality crystals. No particularlimitation is imposed on the kind of flux. The examples include:ammonium halides such as NH₄Cl and NH₄F.HF; alkali metal carbonates suchas Na₂CO₃ and LiCO₃; alkali metal halides such as LiCl, NaCl, KCl, CsCl,LiF, NaF, KF and CsF; alkaline-earth metal halides such as CaCl₂, BaCl₂,SrCl₂, CaF₂, BaF₂, SrF₂, MgCl₂ and MgF₂; alkaline-earth metal oxidessuch as BaO; aluminum halides such as AlF₃; zinc compounds such as zinchalides like ZnCl₂ and ZnF₂, and zinc oxides; compounds of the 15thgroup elements of the periodic table such as Bi₂O₃; and nitrides ofalkali metals, alkaline earth metals or the 13th group elements such asLi₃N, Ca₃N₂, Sr₃N₂, Ba₃N₂ and BN. Other examples of the flux include:halides of rare-earth elements such as LaF₃, LaCl₃, GdF₃, GdCl₃, LuF₃,LuCl₃, YF₃, YCl₃, ScF₃, and ScCl₃; and oxides of rare-earth elementssuch as La₂O₃, Gd₂O₃, Lu₂O₃, Y₂O₃, and Sc₂O₃. Of these, halides arepreferable. Particularly preferable are alkali metal halides,alkaline-earth metal halides, Zn halides, and rare-earth elementhalides. Of these halides, fluorides and chlorides are preferable.

These fluxes can be used either as a single one or as a mixture of twoor more kinds in any combination and in any ratio.

The amount of flux used differs depending on the kind of the materialsor compounds used as the flux. It is preferably in the range of usually0.01 weight % or more, preferably 0.1 weight % or more, more preferably0.3 weight % or more, and usually 20 weight % or less, preferably 5weight % or less, relative to the entire phosphor materials. When theamount of the flux used is too small, the effect of flux may not beexhibited. When the amount of the flux used is too large, the effect offlux may be saturated, or it may be taken up into the host crystals,leading possibly to change in the luminescent color, decrease in thebrightness, and deterioration of the firing furnace.

[4-3. Other Processes]

Steps other than described above can be carried out in the productionmethod (II) according to the present invention if necessary. Theexamples as the steps to be performed on the obtained phosphor include arefiring step, pulverization step, washing step, classification step,surface treatment step, drying step.

Of these, pulverization step, washing step, classification step andsurface treatment step can be performed in the same way as described forthe production method (I) according to the present invention.

The phosphor obtained by a secondary nitriding process may be subjected,if necessary, to a refiring process, in which the phosphor undergoes anadditional heat treatment (refiring treatment) so that the particlesgrow. This may lead to improved phosphor characteristics such as highluminescence of the phosphor due to its particles grown.

In this refiring process, a phosphor can be refired after allowed tocool to room temperature. The heating temperature of such a refiringtreatment is usually 1300° C. or higher, preferably 1400° C. or higher,more preferably 1450° C. or higher, still more preferably 1500° C. orhigher, and usually 1900° C. or lower, preferably 1850° C. or lower,more preferably 1800° C. or lower, still more preferably 1750° C. orlower. Too low a temperature is likely to produce little effect ofgrowing particles of the phosphor. On the other hand, too high atemperature may not only consume unnecessary heating energy but alsodecompose the phosphor. In addition, for preventing decomposition of thephosphor, an extremely high pressure of nitrogen, which is a part ofatmospheric gas, is needed. This tends to result in higher productioncost.

Preferable atmosphere used for refiring the phosphor is basically anitrogen gas atmosphere, inert gas atmosphere, or reducing atmosphere.The inert gas and reducing gas can be used either as a single one or asa combination of two or more kinds in any combination and in any ratio,respectively.

The oxygen concentration in the atmosphere is usually 100 ppm or lower,preferably 50 ppm or lower, more preferably 10 ppm or lower. Whenrefiring is performed in an oxidizing atmosphere such anoxygen-containing gas or air of which oxygen concentration is 250 ppm orhigher, the phosphor may be oxidized and thus the intended phosphor maynot be obtained. However, an atmosphere containing a minute amount ofoxygen such as 0.1 ppm to 10 ppm is preferable, because a phosphor canbe then synthesized at relatively low temperatures.

It is preferable that the pressure at the time of refiring is higherthan atmospheric pressure in order to prevent mixing of atmosphericoxygen. When the pressure is too low, it is possible that a large amountof oxygen mixes in the case of incomplete airtightness of the firinginstrument, leading to deterioration of characteristics of the phosphor,in the same way as the firing step described earlier.

The heating period (retention period of the maximum temperature) of therefiring treatment is usually 1 min or longer, preferably 10 min orlonger, more preferably 30 min or longer, and usually 100 hours orshorter, preferably 24 hours or shorter, more preferably 12 hours orshorter. When the heating period is too short, particle growth tends tobe insufficient. On the other hand, when the heating period is too long,unnecessary heating energy consumption tends to occur and theluminescent characteristics may decrease due to eliminated nitrogen fromthe phosphor surface.

[5. Phosphor-Containing Composition]

The phosphor (I) and phosphor (II) of the present invention can be usedas a mixture with a liquid medium. Particularly when the phosphor (I) orphosphor (II) of the present invention is used for a light emittingdevice or the like, it is preferably used as a dispersion in a liquidmedium, which is then sealed and cured by heat or light. In whatfollows, the phosphor (I) and phosphor (II) of the present inventionwill be referred to simply as “the phosphor of the present invention”when no distinction is made between them. The phosphor of the presentinvention that is dispersed in a liquid medium will be referred to as“the phosphor-containing composition of the present invention” asappropriate.

[5-1. Phosphor]

There is no limitation on the type of the phosphor of the presentinvention to be contained in the phosphor-containing composition of thepresent invention, and any of that can be selected from those describedabove. The phosphor of the present invention to be contained in thephosphor-containing composition of the present invention can be used asa single kind thereof or as a mixture of two or more kinds in anycombination and in any ratio. Furthermore, in the phosphor-containingcomposition of the present invention, a phosphor other than the phosphorof the present invention can be contained, insofar as the advantage ofthe present invention is not significantly impaired.

[5-2. Liquid Medium]

There is no special limitation on the kind of a liquid medium used forthe phosphor-containing composition of the present invention, insofar asthe performance of the phosphor can be sufficient enough to achieve theobject of the present invention. For example, any inorganic materialand/or organic material can be used, insofar as it exhibits liquidcharacteristics under a desired use condition and lets the phosphor ofthe present invention be dispersed preferably without any unfavorablereaction.

Examples of the inorganic materials include metal alkoxide, ceramicprecursor polymer, a solution obtained by hydrolytic polymerization of asolution containing metal alkoxide using a sol-gel method (such as aninorganic material containing siloxane bond).

Examples of the organic materials include thermoplastic resin,thermosetting resin and light curing resin. More specifically, theexamples include: methacrylic resin such as polymethacrylate methyl;styrene resin such as polystyrene, styrene-acrylonitrile copolymer;polycarbonate resin; polyester resin; phenoxy resin; butyral resin;polyvinyl alcohol; cellulose resin such as ethyl cellulose, celluloseacetate and cellulose acetate butyrate; epoxy resin; phenol resin; andsilicone resin.

Of these, a silicon-containing compound can be preferably used as aliquid medium from the standpoint of high heat resistance, high lightresistance and the like, particularly when the phosphor of the presentinvention is used for a high-power light emitting device such as anilluminating device.

Silicon-containing compound means a compound of which molecular containsa silicon atom. Examples thereof include organic materials (siliconematerials) such as polyorganosiloxane, inorganic materials such assilicon oxide, silicon nitride and silicon oxynitride, glass materialssuch as borosilicate, phosphosilicate and alkali silicate. Among them,silicone materials are preferably used from the standpoint of ease inhandling or the like.

The above-mentioned silicone material usually indicates organic polymershaving a siloxane bond as the main chain. Examples thereof includecompounds represented by the following general composition formula (i)and/or mixtures of them.(R¹R²R³SiO_(1/2))_(M)(R⁴R⁵SiO_(2/2))_(D)(R⁶SiO_(3/2))_(T)(SiO_(4/2))_(Q)  formula(i)

In the general composition formula (i), R¹ to R⁶ are each selected fromthe group consisting of organic functional group, hydroxyl group andhydrogen atom. R¹ to R⁶ can be the same as or different from each other.

In addition, M, D, T and Q of the above-mentioned formula (i) are eachnumber of 0 or greater and smaller than 1, and they satisfies M+D+T+Q=1.

The silicone material can be used after being sealed with a liquidsilicone material and cured by heat or light, when used for sealing asemiconductor luminous element.

When categorizing silicone materials based on the curing mechanism, theyusually fall into such categories as addition polymerization-curabletype, polycondensation-curable type, ultraviolet ray-curable type andperoxide vulcanized type. Of these, preferable are additionpolymerization-curable type (addition type silicone resin) andcondensation-curable type (condensing type silicone resin) andultraviolet ray-curable type. In the following, addition type siliconematerial and condensing type silicone material will be explained.

Addition type silicone material represents a material in whichpolyorganosiloxane chain is cross-linked by means of organic additionalbond. Typical examples thereof include a compound having a Si—C—C—Sibond as the crosslinking point, which can be obtained through a reactionbetween vinylsilane and hydrosilane in the presence of an addition typecatalyst such as Pt catalyst. As such compounds, commercially availableones can be used. For example, as concrete commercial names of anaddition polymerization-curable type can be cited “LPS-1400”, “LPS-2410”and “LPS-3400”, manufactured by Shin-Etsu Chemical Co., Ltd.

On the other hand, examples of a condensing type silicone materialinclude a compound having an Si—O—Si bond as the crosslinking point,which can be obtained through hydrolysis and polycondensation of alkylalkoxysilane. Examples thereof include: a polycondensate obtained byperforming hydrolysis and polycondensation of compounds represented bythe following general formula (ii) and/or (iii), and/or an oligomerthereof.M^(m+)X_(n)Y¹ _(m−n)  (ii)(In the formula (ii), M represents at least one element selected fromsilicon, aluminum, zirconium and titanium, X represents a hydrolyzablegroup, Y¹ represents a monovalent organic group, m represents an integerof 1 or larger representing the valence of M, and n represents aninteger of 1 or larger representing the number of X groups, where m≧n.)(M^(s+)X_(t)Y¹ _(s−t−1))_(u)Y²  (iii)(In the formula (iii), M represents at least one element selected fromsilicon, aluminum, zirconium and titanium, X represents a hydrolyzablegroup, Y¹ represents a monovalent organic group, Y² represents au-valent organic group, s represents an integer of 1 or largerrepresenting the valence of M, t represents an integer of 1 or largerand s−1 or smaller, and u represents an integer of 2 or larger.)

The condensing type silicone material may contain a curing catalyst. Asthe curing catalyst, a metal chelate compound can be used preferably,for example. The metal chelate compound preferably contains at least oneof Ti, Ta and Zr, and more preferably contains Zr. The curing catalystsmay be used either as a single kind thereof or as a mixture of more thanone kind in any combination and in any ratio.

As such condensing type silicone material can be used preferably, forexample, semiconductor light emitting device members disclosed inJapanese Patent Laid-Open Publications (Kokai) No. 2007-112973 to No.2007-112975, Japanese Patent Laid-Open Publication (Kokai) No.2007-19459, and Japanese Patent Application No. 2006-176468.

In the following, particularly preferable ones among condensing typesilicone materials will be explained.

Silicone materials generally have such problems as low adhesiveness tothe semiconductor luminous element, the substrate at which the elementis disposed, the package and the like. However, as a silicone materialwith especially high adhesion can be preferably used a condensing typesilicone material having at least one of the following characteristics[1] to [3].

-   [1] The silicon content is 20 weight % or more.-   [2] In the solid Si-nuclear magnetic resonance spectrum (NMR),    measured by a method to be described later in detail, it has at    least one of Si-originated peaks of the following (a) and/or (b).

(a) A peak whose peak top position is in an area of a chemical shift of−40 ppm or more and 0 ppm or less, with reference to tetramethoxysilane,and whose full width at half maximum is 0.3 ppm or more and 3.0 ppm orless.

(b) A peak whose peak top position is in an area of a chemical shift of−80 ppm or more and less than −40 ppm, with reference totetramethoxysilane, and whose full width at half maximum is 0.3 ppm ormore and 5.0 ppm or less.

-   [3] The silanol content is 0.1 weight % or more and 10 weight % or    less.

It is preferable that the silicone material in the present invention hasthe characteristic [1], among the above-mentioned characteristics [1] to[3]. It is more preferable that the silicone material has theabove-mentioned characteristics [1] and [2]. It is particularlypreferable that the silicone material has all the above-mentionedcharacteristics [1] to [3].

In the following, the above-mentioned characteristics [1] to [3] will beexplained.

[5-2-1. Characteristic [1] (Silicon Content)]

The silicon content in the silicone material that is preferable for thepresent invention is usually 20 weight % or more. However, it isparticularly preferably 25 weight % or more, and more particularlypreferably 30 weight % or more. On the other hand, the upper limitthereof is usually 47 weight %, because the silicon content of a glass,consisting only of SiO₂, is 47 weight %.

The silicon content of a silicone material can be calculated based onthe result of inductively coupled plasma spectrometry (inductivelycoupled plasma spectrometry; hereinafter abbreviated as “ICP” whenappropriate) analysis, carried out in accordance with, for example, amethod described below.

{Measurement of Silicon Content}

A silicone material is kept in a platinum crucible in the air at 450° C.for 1 hour and then at 750° C. for 1 hour and at 950° C. for 1.5 hoursfor firing. After removal of carbon components, the small amount ofresidue obtained is added with a 10-fold amount or more of sodiumcarbonate, and then heated by a burner to melt it. Then the meltedproduct is cooled and added with desalted water, being diluted toseveral ppm in silicon, while adjusting pH value to around neutralityusing hydrochloric acid. And then ICP analysis is performed.

[5-2-2. Characteristic [2] (Solid Si-NMR Spectrum)]

When measuring the solid Si-NMR spectrum of a silicone materialpreferable for the present invention, at least one, preferably two ormore of peaks can be observed in the aforementioned peak regions (a)and/or (b), originating from a silicon atom directly bonded with acarbon atom of an organic group.

Summarizing in terms of chemical shifts, in a silicone materialpreferable for the present invention, the full width at half maximum ofthe peak described in (a) is generally smaller than that of the peak of(b) described later, due to smaller constraints of molecular motion.Namely, it is in the range of usually 3.0 ppm or less, preferably 2.0ppm or less, and usually 0.3 ppm or more.

On the other hand, the full width at half maximum of the peak describedin (b) is in the range of usually 5.0 ppm or less, preferably 4.0 ppm orless, and usually 0.3 ppm or more, preferably 0.4 ppm or more.

If the full width at half maximum of a peak observed in the abovechemical shift areas is too large, a state in which constraints ofmolecular motion are large and thus the distortion is large is created,leading possibly to forming a member inferior in heat resistance andweather resistance, and of which cracks are more likely to appear. Forexample when a lot of tetrafunctional silane is used or when largeinternal stress is generated by a rapid drying in the drying process,the range of the full width at half maximum will be larger than theabove range.

If the full width at half maximum of the peak is too small, Si atomsexisting in its environment are not involved in the siloxanecrosslinking. In such a case, for example when trifunctional silaneremains in a non-crosslinked state, the obtained member may be inferiorin heat resistance and weather resistance to materials formed mainly ofsiloxane bonds.

However, even if a peak, of the above-mentioned range of the full widthat half maximum, is observed in an area of −80 ppm or more in a siliconematerial containing a small amount of Si component in a large amount oforganic components, the heat resistance, light resistance and coatingproperties may not be excellent.

The chemical shift value of a silicone material preferable for thepresent invention can be calculated based on the results of a solidSi-NMR measurement performed by, for example, a method described below.Also, the measured data (the full width at half maximum, silanol amountand so on) is analyzed by a method in which each peak is divided andextracted by the waveform separation analysis or the like utilizing, forexample, the Gauss function or Lorentz function.

{Solid Si-NMR Spectrum Measurement and Calculation of the SilanolContent}

When measuring the solid Si-NMR spectrum of a silicone material, thesolid Si-NMR spectrum measurement and the waveform separation analysisare performed under the following conditions. Further, the full width athalf maximum of each peak is determined, for the silicone material,based on the obtained waveform data. In addition, the silanol content isdetermined by comparing the ratio (%) of silicon atoms in silanol to allsilicon atoms, decided from the ratio of peak areas originating fromsilanol to all peak areas, with the silicon content ratio analyzedseparately.

{Device Conditions}

Device: Infinity CMX-400 nuclear magnetic resonance spectroscope,manufactured by Chemagnetics Inc.

²⁹Si resonance frequency: 79.436 MHz

Probe: 7.5 mm φ CP/MAS probe

Temperature: Room temperature

Rotational frequency of sample: 4 kHz

Measurement method: Single pulse method

¹H decoupling frequency: 50 kHz

²⁹Si flip angle: 90°

²⁹Si 90° pulse width: 5.0 μs

Repetition time: 600 s

Total count: 128 times

Observation width: 30 kHz

Broadening factor: 20 Hz

Authentic sample: tetramethoxysilane

For a silicone material, 512 points are taken in as measured data andzero-filled to 8192 points, before Fourier transformation is performed.

{Waveform Separation Analysis Method}

For each peak of the spectrum after Fourier transformation, anoptimization calculation is performed by the nonlinear least squaremethod using the center position, height and full width at half maximumof a peak shape, created by a Lorentz waveform, Gauss waveform or amixture of both, as variable parameters.

For identification of a peak, refer to AIChE Journal, 44(5), p. 1141,1998 or the like.

[5-2-3. Characteristic [3] (Silanol Content)]

The silanol content of a silicone material preferable for the presentinvention is in the range of usually 0.1 weight % or more, preferably0.3 weight % or more, and usually 10 weight % or less, preferably 8weight % or less, more preferably 5 weight % or less. When the silanolcontent is small, the silanol material varies little over time and canbe superior in long-term performance stability, as well as in lowhygroscopicity and low moisture permeability. However, no silanolcontent results only in poor adhesion, and therefore, there is suchappropriate range of the silanol content as described above.

The silanol content of a silicone material can be decided by such methodas described before for {Solid Si-NMR spectrum measurement andcalculation of the silanol content} in [5-2-2. Characteristic [2] (solidSi-NMR spectrum)], for example. In such a method, the ratio (%) ofsilicon atoms in silanol relative to all silicon atoms is determinedfrom the ratio of peak areas originating from silanol relative to allpeak areas by means of the solid Si-NMR spectrum measurement, and then,the silanol content can be calculated by comparing the determinedsilicon ratio with the silicon content analyzed separately.

Since a silicone material preferable for the present invention containsan appropriate amount of silanol, which is bound to a polar portion,usually existing on the device surface, through hydrogen bond, theadhesion develops. The polar portion includes, for example, a hydroxylgroup and oxygen in a metalloxane bond.

In addition, a silicone material preferable for the present inventionusually forms, due to dehydration condensation, a covalent bond with ahydroxyl group on the device surface when heated in the presence of anappropriate catalyst, leading to a development of still firmer adhesion.

With too much content of silanol, on the other hand, thickening in thesystem may make the coating difficult, and also, with increasedactivity, the occurrence of curing before low-boiling point componentsvolatilize by heating may induce a foaming and an increase in internalstress, which may result in crack generations.

[5-3. Content of Liquid Medium]

There is no special limitation on the content of the liquid medium,insofar as the advantage of the present invention is not significantlyimpaired. However, it is usually 50 weight % or more, preferably 75weight % or more, and usually 99 weight % or less, preferably 95 weight% or less, to the whole phosphor-containing composition of the presentinvention. Even a large amount of liquid medium does not induce anyproblems particularly, but in order to achieve desired color coordinate,color rendering index, emission efficiency or the like when it is usedfor a semiconductor light emitting device, it is preferable that theliquid medium is used usually in the above-mentioned proportion. Withtoo small amount of the liquid medium, on the other hand, its handlingmay be difficult due to too little fluidity.

The liquid medium serves mainly as binder, in the phosphor-containingcomposition of the present invention. The liquid medium can be usedeither as a single one or as a mixture of two or more kinds in anycombination and in any ratio. For example, when a silicon-containingcompound is used for the purpose of high heat resistance or lightresistance, other thermosetting resin such as epoxy resin can beincluded to the extent that the durability of the silicon-containingcompound will not be impaired. In such a case, it is preferable that thecontent of the other thermosetting resin is usually 25 weight % orlower, preferably 10 weight % or lower, to the whole amount of theliquid medium, which serves as the binder.

[5-4. Other Component]

In the phosphor-containing composition of the present invention, othercomponents can be contained in addition to the phosphor and liquidmedium, insofar as the advantage of the present invention is notsignificantly impaired. The other components may be used either as asingle kind thereof or as a mixture of more than one kind in anycombination and in any ratio.

[5-5. Advantageous Effect of Phosphor-Containing Composition]

The phosphor-containing composition of the present invention can fix thephosphor of the present invention at a desired location easily. Forexample when the phosphor-containing composition of the presentinvention is used for a light emitting device, the phosphor of thepresent invention can be easily fixed at a desired location by formingthe phosphor-containing composition of the present invention at adesired location and curing the liquid medium for sealing the phosphorof the present invention with the liquid medium.

[6. Light Emitting Device]

The light emitting device of the present invention (hereinafter referredto as “the light emitting device” as appropriate) comprises a firstluminous body (excitation light source) and a second luminous body whichemits visible light when irradiated with light from the first luminousbody. The light emitting device comprises one or more kinds of thephosphor of the present invention as the first phosphor in the secondluminous body.

The light emitting device of the present invention can be of any knowndevice configuration specifically in which an excitation light source tobe described later is used as the first luminous body and the phosphoradjusted in its kind or content is used as the second luminous body.With such a configuration, the light emitting device of the presentinvention can emit any color of light.

For example, even an emission spectrum similarly to that of so-calledpseudo-white (for example, a luminescent color of the light emittingdevice in which a blue LED and a yellow phosphor are combined) can beobtained by combining an excitation light source emitting blue light anda phosphor of the present invention emitting yellow green to orangefluorescence (namely, yellow green to orange phosphor). Furthermore, byincorporating a phosphor emitting red fluorescence (red phosphor) and,if necessary, a green phosphor in that white light emitting device, alight emitting device that is extremely excellent in red color renderingor emits a warm white light can be realized. A white light emittingdevice can also be produced by combining an excitation light sourceemitting near-ultraviolet light, a phosphor emitting blue fluorescence(blue phosphor), a green phosphor, and a red phosphor.

In this context, the white color of the white light emitting deviceincludes all of (Yellowish) White, (Greenish) White, (Bluish) White,(Purplish) White and White, which are defined in JIS Z 8701. Of these,preferable is White.

Moreover, light emitting devices emitting any color of light can beproduced by combining, as needed, a green phosphor (a phosphor emittinggreen fluorescence), blue phosphor, orange to red phosphor, or otherkind of yellow phosphor and adjusting the kinds or the contents of thephosphors.

The phosphor of the present invention can be used either as a singlekind or as a mixture of two or more kinds in any combination and in anyratio.

The emission spectrum peak in the green region, in the emission spectrumof light emitting device of the present invention, preferably exists inthe wavelength range of from 515 nm to 535 nm. The emission spectrumpeak in the red region thereof preferably exists in the wavelength rangeof from 580 nm to 680 nm. The emission spectrum peak in the blue regionthereof preferably exists in the wavelength range of from 430 nm to 480nm. The emission spectrum peak in the yellow region thereof preferablyexists in the wavelength range of from 540 nm to 580 nm.

The emission spectrum of the light emitting device can be measured in aroom of which temperature is kept at 25±1° C. with energization of 20mA, using a software for measuring color and illumination intensity,manufactured by Ocean Optics, Inc., and a spectroscope of USB2000 series(integrating sphere version). From this emission spectrum data in thewavelength region of 380 nm to 780 nm, can be calculated thechromaticity value (x, y, z) as color coordinates of xyz colorimetricsystem, defined in JIS Z8701. In this case, the relational expression ofx+y+z=1 holds. In the present Description, the aforementioned XYZcolorimetric system is occasionally referred to as XY colorimetricsystem and the value thereof is usually represented as (x,y).

Emission efficiency can be determined by calculating the total luminousflux from the results of emission-spectrum measurement using a lightemitting device mentioned earlier and then dividing the lumen value (lm)obtained by the power consumption (W). The power consumption can beobtained as the product of the current value and the voltage value,which is measured using True RMS Multimeters Model 187 and 189manufactured by Fluke Corporation while 20-mA energization.

The general color rendering index (Ra) and special color rendering indexR9 of light emitting device of the present invention take the values ofusually 80 or larger, preferably 90 or larger, and more preferably 95 orlarger.

[6-1. Configuration of Light Emitting Device (Luminous Body)]

(First Luminous Body)

The first luminous body of the light emitting device of the presentinvention emits light for exciting the second luminous body to bedescribed later.

The first luminous body has no particular limitation in its luminouswavelength, insofar as it overlaps the absorption wavelength of thesecond luminous body to be described later, and therefore, variousluminous bodies with wide range of luminous wavelength regions areapplicable. Usually a luminous body having luminous wavelength of fromultraviolet region to blue region is used. Among them, particularlypreferable are luminous bodies having luminous wavelength of fromnear-ultraviolet region to blue region.

It is preferable that the luminous peak wavelength of the first luminousbody usually has a concrete value of 200 nm or longer. Among them, it ispreferable that, when a near-ultraviolet light is used as the excitationlight, a luminous body with a peak luminous wavelength of usually 300 nmor longer, preferably 330 nm or longer, more preferably 360 nm orlonger, and usually 420 nm or shorter is used. When a blue light is usedas the excitation light, it is preferable that a luminous body with apeak luminous wavelength of usually 420 nm or longer, preferably 430 nmor longer, and usually 500 nm or shorter, preferably 480 nm or shorteris used. Both of these conditions are required from the standpoint ofcolor purity of the light emitting device.

As the first luminous body, a semiconductor luminous element isgenerally used. Concretely, an LED, semiconductor laser diode(hereinafter, abbreviated as “LD” as appropriate) or the like can beused. Other examples of the luminous body that can be used as the firstluminous body include an organic electroluminescence luminous element,inorganic electroluminescence luminous element or the like. However, theluminous body that can be used as the first luminous body is notrestricted to those exemplified in the present Description.

Among them, a GaN-based LED and GaN-based LD, using a GaN-based compoundsemiconductor, are preferable for the first luminous body. This isbecause a GaN-based LED and GaN-based LD have light output and externalquantum efficiency far greater than those of an SiC-based LED and thelike that emit the same range of light and therefore they can give verybright luminescence with very low electric power when used incombination with the above-mentioned phosphor. For example, whenapplying current load of 20 mA, a GaN-based LED and GaN-based LD usuallyhave emission intensity 100 times or higher than that of an SiC-basedones. As GaN-based LED or GaN-based LD, one having an Al_(x)Ga_(y)Nluminous layer, GaN luminous layer or In_(x)Ga_(y)N luminous layer ispreferable. Among the GaN-based LEDs, one having an In_(x)Ga_(y)Nluminous layer is particularly preferable due to its remarkably highemission intensity, and one having a multiple quantum well structure ofthe In_(x)Ga_(y)N layer and GaN layer is particularly preferable alsodue to its remarkably high emission intensity.

In the above description, the X+Y usually takes a value in the range of0.8 to 1.2. A GaN-based LED having a such kind of luminous layer that isdoped with Zn or Si or without any dopant is preferable for the purposeof adjusting the luminescent characteristics.

A GaN-based LED contains, as its basic components, a such kind ofluminous layer, p layer, layer, electrode and substrate. Among them, aGaN-based LED having such a heterostructure as sandwiching the luminouslayer with n type and p type of Al_(x)Ga_(y)N layers, GaN layers,In_(x)Ga_(y)N layers or the likes is preferable, from the standpoint ofhigh emission efficiency. Moreover, the one whose heterostructure isreplaced by a quantum well structure is more preferable because it canshow higher emission efficiency.

The first luminous body can be used either as a single one or as amixture of two or more of them in any combination and in any ratio.

(Second Luminous Body)

The second luminous body of the light emitting device of the presentinvention is a luminous body which emits visible light when irradiatedwith light from the above-mentioned first luminous body. It comprisesthe aforementioned phosphor of the present invention as the firstphosphor, as well as the second phosphor (orange to red phosphor, greenphosphor, blue phosphor, yellow phosphor and the like) to be describedlater as appropriate depending on its use of the like. The secondluminous body is formed, for example, so that the first and the secondphosphors are dispersed in a sealing material.

There is no special limitation on the composition of the other phosphorthan the phosphor of the present invention, which is used in the secondluminous body. The examples include compounds incorporating a hostcrystal, such as a metal oxide typified by Y₂O₃, YVO₄, Zn₂SiO₄, Y₃Al₅O₁₂and Sr₂SiO₄, a metal nitride typified by Sr₂Si₅N₈, phosphate typified byCa₅(PO₄)₃Cl, a sulfide typified by ZnS, SrS and CaS and an oxysulfidetypified by Y₂O₂S and La₂O₂S, with an activation element or coactivationelement, such as an ion of a rare earth metal including Ce, Pr, Nd, Pm,Sm, Eu, Tb, Dy, Ho, Er, Tm or Yb, or a metal ion of Ag, Cu, Au, Al, Mnor Sb.

Preferable examples of the host crystal include: sulfides such as(Zn,Cd)S, SrGa₂S₄, SrS and ZnS; oxysulfides such as Y₂O₂S; aluminatessuch as (Y,Gd)₃Al₅O₁₂, YAlO₃, BaMgAl₁₀O₁₇, (Ba,Sr)(Mg,Mn)Al₁₀O₁₇,(Ba,Sr,Ca)(Mg,Zn,Mn)Al₁₀O₁₇, BaAl₁₂O₁₈, CeMgAl₁₁O₁₉, (Ba,Sr,Mg)O.Al₂O₃,BaAl₂Si₂O₈, SrAl₂O₄, Sr₄Al₁₄O₂₅ and Y₃Al₅O₁₂; silicates such as Y₂SiO₅and Zn₂SiO₄; oxides such as SnO₂ and Y₂O₃; borates such as GdMgB₅O₁₀ and(Y,Gd)BO₃; halophosphates such as Ca₁₀(PO₄)₆(F,Cl)₂ and(Sr,Ca,Ba,Mg)₁₀(PO₄)₈Cl₂; and phosphates such as Sr₂P₂O₇ and (La,Ce)PO₄.

No particular limitation is imposed on the element compositions of theabove-mentioned host crystal, and activation element or coactivationelement. Partial substitution with an element of the same group ispossible. Any phosphor obtained can be used so long as it absorbs lightin the near-ultraviolet to visible region and emits visible light.

More concretely, those listed below can be used as phosphor. However,the lists are just examples and phosphors that can be used in thepresent invention are not limited to those examples. In the followingexamples, phosphors with different partial structure are shownabbreviated as a group for the sake of convenience, as mentionedearlier.

(First Phosphor)

The second luminous body in the light emitting device of the presentinvention contains at least the above-mentioned phosphor of the presentinvention as the first phosphor. The phosphor of the present inventioncan be used either as a single kind or as a mixture of two or more kindsin any combination and in any ratio.

In addition, the first phosphor may contain, in addition to the phosphorof the present invention, a phosphor (a combined same-color phosphor)emitting a fluorescence of the same color as that of the phosphor of thepresent invention. For example when the phosphor of the presentinvention is a green phosphor, another kind of green phosphor can beused as the first phosphor in combination with the phosphor of thepresent invention. When the phosphor of the present invention is aorange or red phosphor, another kind of orange to red phosphor can beused as the first phosphor in combination with the phosphor of thepresent invention. When the phosphor of the present invention is a bluephosphor, another kind of blue phosphor can be used as the firstphosphor in combination with the phosphor of the present invention. Inaddition, when the phosphor of the present invention is a yellowphosphor, another kind of yellow phosphor can be used as the firstphosphor in combination with the phosphor of the present invention.

There is no limitation on these phosphors, insofar as the advantage ofthe present invention is not significantly impaired.

(Green Phosphor)

It is preferable that the wavelength of emission peak of such a greenphosphor is in the range of usually longer than 500 nm, particularly 510nm or longer, further particularly 515 nm or longer, and usually 550 nmor shorter, particularly 540 nm or shorter, further particularly 535 nmor shorter. When that wavelength of emission peak λ_(p) is too short,the color tends to be bluish green. On the other hand, when it is toolong, the color tends to be yellowish green. In both cases, thecharacteristics of its green light may deteriorate.

The full width at half maximum of emission peak of such a green phosphoris usually in the range of 40 nm to 80 nm.

The external quantum efficiency of such a green phosphor is usually 60%or higher, and preferably 70% or higher. The weight-average mediandiameter thereof is usually 1 μm or larger, preferably 5 μm or larger,more preferably 10 μm or larger, and usually 30 μm or smaller,preferably 20 μm or smaller, more preferably 15 μm or smaller.

Examples of such a green phosphor include an europium-activated alkalineearth silicon oxynitride phosphor represented by(Mg,Ca,Sr,Ba)Si₂O₂N₂:Eu, which is constituted by fractured particleshaving a fractured surface and emits light in the green region.

Other examples of such green phosphor include: Eu-activated aluminatephosphor such as Sr₄Al₁₄O₂₅:Eu and (Ba,Sr,Ca)Al₂O₄:Eu; Eu-activatedsilicate phosphor such as (Sr,Ba)Al₂Si₂O₈:Eu, (Ba,Mg)₂SiO₄:Eu,(Ba,Sr,Ca,Mg)₂SiO₄:Eu, (Ba,Sr,Ca)₂(Mg,Zn)Si₂O₇:Eu and phosphor;Ce,Tb-activated silicate phosphor such as Y₂SiO₅:Ce,Tb; Eu-activatedborophosphate phosphor such as Sr₂P₂O₇—Sr₂B₂O₅:Eu; Eu-activatedhalosilicate phosphor such as Sr₂Si₃O₈-2SrCl₂:Eu; Mn-activated silicatephosphor such as Zn₂SiO₄:Mn; Tb-activated aluminate phosphor such asCeMgAl₁₁O₁₉:Tb and Y₃Al₅O₁₂:Tb; Tb-activated silicate phosphor such asCa₂Y₈(SiO₄)₆O₂:Tb and La₃Ga₅SiO₁₄:Tb; Eu,Tb,Sm-activated thiogalatephosphor such as (Sr,Ba,Ca)Ga₂S₄:Eu,Tb,Sm; Ce-activated aluminatephosphor such as Y₃(Al,Ga)₅O₁₂:Ce and(Y,Ga,Tb,La,Sm,Pr,Lu)₃(Al,Ga)₅O₁₂:Ce; Ce-activated silicate phosphorsuch as Ca₃Sc₂Si₃O₁₂:Ce and Ca₃(Sc,Mg,Na,Li)₂Si₃O₁₂:Ce; Ce-activatedoxide phosphor such as CaSc₂O₄:Ce; Eu-activated oxynitride phosphor suchas Eu-activated β-sialon; Eu,Mn-activated aluminate phosphor such asBaMgAl₁₀O₁₇:Eu, Mn; Eu-activated aluminate such as SrAl₂O₄:Eu;Tb-activated oxysulfide phosphor such as (La,Gd,Y)₂O₂S:Tb;Ce,Tb-activated phosphate phosphor such as LaPO₄:Ce,Tb; sulfide phosphorsuch as ZnS:Cu,Al and ZnS:Cu,Au,Al; Ce,Tb-activated borate phosphor suchas (Y,Ga,Lu,Sc,La)BO₃:Ce,Tb, Na₂Gd₂B₂O₇:Ce,Tb and(Ba,Sr)₂(Ca,Mg,Zn)B₂O₆:K,Ce,Tb; Eu,Mn-activated halosilicate phosphorsuch as Ca₈Mg(SiO₄)₄Cl₂:Eu,Mn; Eu-activated thioaluminate phosphor orthiogallate phosphor such as (Sr,Ca,Ba)(Al,Ga,In)₂S₄:Eu; Eu,Mn-activatedhalosilicate phosphor such as (Ca,Sr)₈(Mg,Zn)(SiO₄)₄Cl₂:Eu,Mn; andEu-activated oxynitride such as M₃Si₆O₉N₄:Eu and M₃Si₆O₁₂N₂:Eu (here, Mrepresents alkaline earth metal element).

Also applicable as the green phosphor are fluorescent dyes such aspyridine-phthalimide condensed derivative, benzoxadinone compound,quinazoline compound, coumarine compound, quinophthalone compound,naphthalimide compound, and organic phosphors such as terbium complex.

The green phosphor exemplified above can be used either as a single kindor as a mixture of two or more kinds in any combination and in anyratio.

(Orange to Red Phosphor)

It is preferable that the wavelength of emission peak of such an orangeto red phosphor is in the range of usually 570 nm or longer, preferably580 nm or longer, more preferably 585 nm or longer, and usually 780 nmor shorter, preferably 700 nm or shorter, more preferably 680 nm orshorter.

Examples of such an orange to red phosphor include an europium-activatedalkaline earth silicon nitride phosphor represented by(Mg,Ca,Sr,Ba)₂Si₅N₈:Eu, which is constituted by fractured particleshaving red fractured surfaces and emits light in red region, and aneuropium-activated rare-earth oxychalcogenide phosphor represented by(Y,La,Gd,Lu)₂O₂S:Eu, which is constituted by growing particles having anearly spherical shapes typical of regular crystal growth and emitslight in red region.

The full width at half maximum of emission peak of such a red phosphoris usually in the range of 1 nm to 100 nm.

The external quantum efficiency of such a red phosphor is usually 60% orhigher, and preferably 70% or higher. The weight-average median diameterthereof is usually 1 μm or larger, preferably 5 μm or larger, morepreferably 10 μm or larger, and usually 30 μm or smaller, preferably 20μm or smaller, more preferably 15 μm or smaller.

Also applicable in the present embodiment is an phosphor containingoxynitride and/or oxysulfide which include at least one element selectedfrom the group consisting of Ti, Zr, Hf, Nb, Ta, W and Mo, described inJapanese Patent Laid-Open Publication (Kokai) No. 2004-300247, andcontaining an oxynitride having an α-sialon structure in which all orpart of Al elements are replaced by Ga elements. These are phosphorswhich contain oxynitride and/or oxysulfide.

Other examples of the red phosphor include: Eu-activated oxysulfidephosphor such as (La,Y)₂O₂S:Eu; Eu-activated oxide phosphor such asY(V,P)O₄:Eu and Y₂O₃:Eu; Eu,Mn-activated silicate phosphor such as(Ba,Mg)₂SiO₄:Eu,Mn and (Ba,Sr,Ca,Mg)₂SiO₄:Eu,Mn; Eu-activated tungstatesuch as LiW₂O₈:Eu, LiW₂O₈:Eu,Sm, Eu₂W₂O₉, Eu₂W₂O₉:Nb, Eu₂W₂O₉: Sm;Eu-activated sulfide phosphor such as (Ca,Sr)S:Eu; Eu-activatedaluminate phosphor such as YAlO₃:Eu; Eu-activated silicate phosphor suchas Ca₂Y₉(SiO₄)₆O₂:Eu, LiY₉(SiO₄)₆O₂:Eu, (Sr,Ba,Ca)₃SiO₅:Eu andSr₂BaSiO₅:Eu; Ce-activated aluminate phosphor such as (Y,Gd)₃Al₅O₁₂:Ceand (Tb,Gd)₃Al₅O₁₂:Ce; Eu-activated oxide, nitride or oxynitridephosphor such as (Mg,Ca,Sr,Ba)₂Si₅(N,O)₉:Eu, (Mg,Ca,Sr,Ba)Si(N,O)₂:Euand (Mg,Ca,Sr,Ba)AlSi(N,O)₃:Eu; Eu, Mn-activated halophosphate phosphorsuch as (Sr,Ca,Ba,Mg)₁₀(PO₄)₆Cl₂:Eu,Mn; Eu, Mn-activated silicatephosphor such as Ba₃MgSi₂O₈:Eu,Mn and (Ba,Sr,Ca,Mg)₃(Zn,Mg)Si₂O₈:Eu,Mn;Mn-activated germanate phosphor such as 3.5MgO.0.5MgF₂.GeO₂:Mn;Eu-activated oxynitride phosphor such as Eu-activated α-sialon;Eu,Bi-activated oxide phosphor such as (Gd,Y,Lu,La)₂O₃:Eu,Bi;Eu,Bi-activated oxysulfide phosphor such as (Gd,Y,Lu,La)₂O₂S:Eu,Bi;Eu,Bi-activated vanadate phosphor such as (Gd,Y,Lu,La)VO₄:Eu,Bi;Eu,Ce-activated sulfide phosphor such as SrY₂S₄:Eu,Ce; Ce-activatedsulfide phosphor such as CaLa₂S₄:Ce; Eu,Mn-activated phosphate phosphorsuch as (Ba,Sr,Ca)MgP₂O₇:Eu,Mn and (Sr,Ca,Ba,Mg,Zn)₂P₂O₇:Eu,Mn;Eu,Mo-activated tungstate phosphor such as (Y,Lu)₂WO₆:Eu,Mo;Eu,Ce-activated nitride phosphor such as (Ba,Sr,Ca)_(x)Si_(y)N_(z):Eu,Ce(x,y,z being an integer of 1 or larger); Eu,Mn-activated halophosphatephosphor such as (Ca,Sr,Ba,Mg)₁₀(PO₄)₆(F,Cl,Br,OH):Eu,Mn; andCe-activated silicate phosphor such as((Y,Lu,Gd,Tb)_(1−x−y)Sc_(x)Ce_(y))₂(Ca,Mg)_(1−r)(Mg,Zn)_(2+r)Si_(z−q)Ge_(q)O_(12+δ).

Also applicable examples of the red phosphor include: red organicphosphor consisting of rare-earth ion complex containing anions of suchas β-diketonate, β-diketone, aromatic carboxylic acid or Bronsted acidas ligands, perylene pigment (for example,dibenzo{[f,f′]-4,4′,7,7′-tetraphenyl}diindeno[1,2,3-cd:1′,2′,3′-lm]perylene),anthraquinone pigment, lake pigment, azo pigment, quinacridone pigment,anthracene pigment, isoindoline pigment, isoindolinone pigment,phthalocyanine pigment, triphenylmethane series basic dye, indanthronepigment, indophenol pigment, cyanine pigment and dioxazine pigment.

Among them, it is preferable that the red phosphor contains(Ca,Sr,Ba)₂Si₅(N,O)₈:Eu, (Ca,Sr,Ba)Si(N,O)₂:Eu, (Ca,Sr,Ba)AlSi(N,O)₃:Eu,(Ca,Sr,Ba)AlSi(N,O)₃:Ce, (Sr,Ba)₃SiO₅:Eu, (Ca,Sr)S:Eu, (La,Y)₂O₂S:Eu orEu complex. It is more preferable that it contains(Ca,Sr,Ba)₂Si₅(N,O)₈:Eu, (Ca,Sr,Ba)Si(N,O)₂:Eu, (Ca,Sr,Ba)AlSi(N,O)₃:Eu,(Ca,Sr,Ba)AlSi(N,O)₃:Ce, (Sr,Ba)₃SiO₅:Eu, (Ca,Sr)S:Eu, (La,Y)₂O₂S:Eu,β-diketone Eu complex such as Eu(dibenzoylmethane)₃.1,10-phenanthrolinecomplex or carboxylic acid Eu complex. Of these, especially preferableare (Ca,Sr,Ba)₂Si₅(N,O)₈:Eu, (Sr,Ca)AlSi(N,O):Eu and (La,Y)₂O₂S:Eu.

Among the above examples, a phosphor that can be preferably used as theorange phosphor is (Sr,Ba)₃SiO₅:Eu.

Such an orange to red phosphor may be used either as a single kindthereof or as a mixture of more than one kind in any combination and inany ratio.

(Blue Phosphor)

It is preferable that the wavelength of emission peak of such a bluephosphor is in the range of usually 420 nm or longer, preferably 430 nmor longer, more preferably 440 nm or longer, and usually 490 nm orshorter, preferably 480 nm or shorter, more preferably 470 nm orshorter, further preferably 460 nm or shorter.

The full width at half maximum of emission peak of such a blue phosphoris usually in the range of 20 nm to 80 nm.

The external quantum efficiency of such a blue phosphor is usually 60%or higher, and preferably 70% or higher. The weight-average mediandiameter thereof is usually 1 μm or larger, preferably 5 μm or larger,more preferably 10 μm or larger, and usually 30 μm or smaller,preferably 20 μm or smaller, more preferably 15 μm or smaller.

Examples of such a blue phosphor include: europium-activated bariummagnesium aluminate phosphors represented by (Ba,Sr,Ca)MgAl₁₀O₁₇:Eu,which is constituted by growing particles having a nearly hexagonalshape typical of regular crystal growth and emits light in the blueregion, europium-activated calcium halphosphate phosphors represented by(Mg,Ca,Sr,Ba)₅(PO₄)₃(Cl,F):Eu, which is constituted by growing particleshaving a nearly spherical shape typical of regular crystal growth andemits light in the blue region, europium-activated alkaline earthchloroborate phosphors represented by (Ca,Sr,Ba)₂B₅O₉Cl:Eu, which isconstituted by growing particles having a nearly cubic shape typical ofregular crystal growth and emits light in the blue region, andeuropium-activated alkaline earth aluminate phosphors represented by(Sr,Ca,Ba)Al₂O₄:Eu or (Sr,Ca,Ba)₄Al₁₄O₂₅:Eu, which is constituted byfractured particles having fractured surfaces and emits light in theblue green region.

Other examples of such a blue phosphor include: Sn-activated phosphatephosphor such as Sr₂P₂O₇:Sn; Eu-activated aluminate phosphor such as(Sr,Ca,Ba)Al₂O₄:Eu or (Sr,Ca,Ba)₄Al₁₄O₂₅:Eu, BaMgAl₁₀O₁₇:Eu,(Ba,Sr,Ca)MgAl₁₀O₁₇:Eu, BaMgAl₁₀O₁₇:Eu,Tb,Sm and BaAl₈O₁₃:Eu;Ce-activated thiogalate phosphor such as SrGa₂S₄:Ce and CaGa₂S₄:Ce;Eu,Mn-activated aluminate phosphor such as (Ba,Sr,Ca)MgAl₁₀O₁₇:Eu,Mn;Eu-activated halophosphate phosphor such as (Sr,Ca,Ba,Mg)₁₀(PO₄)₆Cl₂:Euand (Ba,Sr,Ca)₅(PO₄)₃(Cl,F,Br,OH):Eu,Mn,Sb; Eu-activated silicatephosphor such as BaAl₂Si₂O₈:Eu, (Sr,Ba)₃MgSi₂O₈:Eu; Eu-activatedphosphate phosphor such as Sr₂P₂O₇:Eu; sulfide phosphor such as ZnS:Agand ZnS:Ag,Al; Ce-activated silicate phosphor such as Y₂SiO₅:Ce;tungstate phosphor such as CaWO₄; Eu,Mn-activated borophosphate phosphorsuch as (Ba,Sr,Ca)BPO₅:Eu,Mn, (Sr,Ca)₁₀(PO₄)₆.nB₂O₃:Eu and2SrO.0.84P₂O₅.0.16B₂O₃:Eu; Eu-activated halosilicate phosphor such asSr₂Si₃O₈.2SrCl₂:Eu; Eu-activated oxynitride phosphor such asSrSi₉Al₁₉ON₃₁:Eu and EuSi₉Al₁₉ON₃₁; and Ce-activated oxynitride phosphorsuch as La_(1−x)Ce_(x)Al(Si_(6−z)Al_(z))(N_(10−z)O_(z)) (here, x and zare numbers satisfying 0≦x≦1 and 0≦z≦6, respectively) andLa_(1−x−y)Ce_(x)Ca_(y)Al(Si_(6−z)Al_(z))(N_(10−z)O_(z)) (here, x, y andz are numbers satisfying 0≦x≦1, 0≦y≦1 and 0≦z≦6, respectively).

Also applicable as the blue phosphor are, for example, fluorescent dyessuch as naphthalimide compound, benzoxazole compound, styryl compound,coumarine compound, pyrazoline compound and triazole compound, andorganic phosphors such as thlium complex.

Among them, it is preferable that the blue phosphor contains(Ca,Sr,Ba)MgAl₁₀O₁₇:Eu, (Sr,Ca,Ba,Mg)₁₀(PO₄)₆(Cl,F)₂:Eu or(Ba,Ca,Mg,Sr)₂SiO₄:Eu. It is more preferable that it contains(Ca,Sr,Ba)MgAl₁₀O₁₇:Eu, (Sr,Ca,Ba,Mg)₁₀(PO₄)₆(Cl,F)₂:Eu or(Ba,Ca,Sr)₃MgSi₂O₈:Eu. It is still more preferable that it containsBaMgAl₁₀O₁₇:Eu, Sr₁₀(PO₄)₆(Cl,F)₂:Eu or Ba₃MgSi₂O₈:Eu. Of these,(Sr,Ca,Ba,Mg)₁₀(PO₄)₆Cl₂:Eu or (Ca,Sr,Ba)MgAl₁₀O₁₇:Eu is particularlypreferable in uses for an illuminating device and a display.

Such a blue phosphor may be used either as a single kind thereof or as amixture of more than one kind in any combination and in any ratio.

(Yellow Phosphor)

It is preferable that the wavelength of emission peak of such a yellowphosphor is in the range of usually 530 nm or longer, preferably 540 nmor longer, more preferably 550 nm or longer, and usually 620 nm orshorter, preferably 600 nm or shorter, more preferably 580 nm orshorter.

The full width at half maximum of emission peak of such a yellowphosphor is usually in the range of 60 nm to 200 nm.

The external quantum efficiency of such a yellow phosphor is usually 60%or higher, and preferably 70% or higher. The weight-average mediandiameter thereof is usually 1 μm or larger, preferably 5 μm or larger,more preferably 10 μm or larger, and usually 30 μm or smaller,preferably 20 μm or smaller, more preferably 15 μm or smaller.

Examples of such a yellow phosphor include various phosphors of such asoxide, nitride, oxynitride, sulfide and oxysulfide.

Particularly preferable examples include garnet phosphors having garnetstructures, represented by RE₃M₅O₁₂:Ce (here, RE indicates at least oneelement selected from the group consisting of Y, Tb, Gd, Lu and Sm, Mindicates at least one element selected from the group consisting of Al,Ga and Sc) and M^(a) ₃M^(b) ₂M^(c) ₃O₁₂:Ce (here, M^(a), M^(b) and M^(c)are divalent, trivalent and tetravalent metal element respectively), forexample; orthosilicate phosphors represented by AE₂M^(d)O₄:Eu (here, AEindicates at least one element selected from the group consisting of Ba,Sr, Ca, Mg and Zn, M^(d) indicates Si and/or Ge), for example;oxynitride phosphors in which a part of the oxygen, contained in theabove types of phosphors as constituent element, are substituted bynitrogen; and Ce-activated nitride phosphors having CaAlSiN₃ structuressuch as AEAlSi(N,O)₃:Ce (here, AE indicates at least one elementselected from the group consisting of Ba, Sr, Ca, Mg and Zn).

Also applicable as the yellow phosphor are: Eu-activated phosphorsincluding sulfides such as CaGa₂S₄:Eu, (Ca,Sr)Ga₂S₄:Eu and(Ca,Sr)(Ga,Al)₂S₄:Eu; and oxynitrides having saialon structure such asCa_(x)(Si,Al)₁₂(O,N)₁₆:Eu.

As other examples of the yellow phosphor can be cited fluorescent dyessuch as brilliant sulfoflavine FF (Color Index Number 56205), basicyellow HG (Color Index Number 46040), eosine (Color Index Number 45380)and rhodamine 6G (Color Index Number 45160).

Such a yellow phosphor may be used either as a single kind thereof or asa mixture of more than one kind in any combination and in any ratio.

(Second Phosphor)

The second luminous body of the light emitting device of the presentinvention may contain another phosphor (namely, a second phosphor) inaddition to the above-mentioned first phosphor, depending on its use.The second phosphor is a phosphor having a different wavelength ofemission peak from that of the first phosphor. Such a second phosphor isusually used for adjusting color tone of light emission of the secondluminous body. Therefore, as the second phosphor, a phosphor emitting adifferent-color fluorescence from the first phosphor is often used.

As described above, when a green phosphor is used as the first phosphor,a phosphor other than green phosphor, such as orange to red phosphor,blue phosphor, or yellow phosphor, is used as the second phosphor. Whenan orange to red phosphor is used as the first phosphor, a phosphorother than orange to red phosphor, such as green phosphor, bluephosphor, or yellow phosphor, is used as the second phosphor. When ablue phosphor is used as the first phosphor, a phosphor other than bluephosphor, such as green phosphor, orange to red phosphor, or yellowphosphor, is used as the second phosphor. When a yellow phosphor is usedas the first phosphor, a phosphor other than yellow phosphor, such asgreen phosphor, orange to red phosphor, or blue phosphor, is used as thesecond phosphor.

Examples of such green, orange to red, blue and yellow phosphors includethe same phosphors listed above in the chapter of the first phosphor.

It is preferable that the weight-average median diameter of the secondphosphor used for the light emitting device of the present invention isin the range of usually 10 μm or larger, preferably 12 μm or larger, andusually 30 μm or smaller, preferably 25 μm or smaller. When theweight-average median diameter is too small, the brightness tends todecrease and the phosphor particles tend to aggregate. On the otherhand, the weight-average median diameter is too large, unevenness incoating, clogging in a dispenser or the like tend to occur.

(Combination of Second Phosphors)

Since the phosphor of the present invention usually emits a yellow greento orange light, it can realize a white light emitting device when usedwith a blue light emitting first luminous body (which usually has anemission peak in the wavelength range of 420 nm or longer and 500 nm orshorter). The color rendering can be enhanced and the color tone can beadjusted, by adjusting the wavelength of emission peak of the firstluminous body or mixing a second phosphor as appropriate. The secondphosphor can be used either as a single kind thereof or as a mixture oftwo or more kinds in any combination and in any ratio. There is nospecial limitation on the ratio between the first phosphor and thesecond phosphor, insofar as the advantage of the present invention isnot significantly impaired. Accordingly, the amount of the secondphosphor used, as well as the combination and the mixing ratio of thesecond phosphors used, can be specified arbitrarily according to the useor the like of the light emitting device.

The phosphor of the present invention can be used as a mixture withanother phosphor (in this context, “mixture” does not necessarily meanto blend the phosphors with each other, but means to use different kindsof phosphors in combination). Among them, the combined use of phosphorsdescribed above will provide a preferable phosphor mixture. There is nospecial limitation on the kind or the ratio of the phosphors mixed.

One of such a preferable combination is as follows. A blue lightemitting luminous body (which usually has an emission peak in thewavelength range of 420 nm or longer and 500 nm or shorter) is used asthe first luminous body. The phosphor of the present invention is usedas the first phosphor. An orange to red phosphor (which usually has anemission peak in the wavelength range of 570 nm or longer and 780 nm orshorter) and/or a green phosphor (which usually has an emission peak inthe wavelength range of 500 nm or longer and 550 nm or shorter) are usedas the second phosphor.

Another such preferable combination is as follows. A near-ultravioletlight emitting luminous body (which usually has an emission peak in thewavelength range of 300 nm or longer and 420 nm or shorter) is used asthe first luminous body. The phosphor of the present invention is usedas the first phosphor. A blue phosphor (which usually has an emissionpeak in the wavelength range of 420 nm or longer and 490 nm or shorter)is used as the second phosphor. An orange to red phosphor and/or a greenphosphor may be added to this combination.

(Sealing Material)

In the light emitting device of the present invention, theabove-mentioned first and/or second phosphors are usually used by beingdispersed in a liquid medium, a sealing member, which seals thephosphors by being cured by heat or light.

Examples of that liquid medium include the same ones as listed earlierin the aforementioned section of [5. Phosphor-containing composition].

The liquid medium may contain a metal element that can be a metal oxidehaving high refractive index, for the purpose of adjusting therefractive index of the sealing member. As examples of a metal elementproviding metal oxide having high refractive indexes can be cited Si,Al, Zr, Ti, Y, Nb and B. These metal elements can be used as a singlekind or as a mixture of two or more kinds in any combination and in anyratio.

There is no special limitation on the state of existence of such metalelements, insofar as the transparency of the sealing member does notdeteriorate. For example, they may exist as a uniform grass layer ofmetalloxane bonds or as particles in the sealing member. When they existin a state of particles, the structure inside the particles may beeither amorphous or crystal structure. However, for higher refractiveindex, the crystal structure is preferable. In such a case, the particlediameter thereof is usually equal to or smaller than the luminouswavelength of a semiconductor luminous element, and preferably 100 nm orsmaller, more preferably 50 nm or smaller, particularly preferably nm orsmaller, in order not to impair the transparency of the sealing member.The above-mentioned metal elements in a state of particles contained inthe sealing member can be obtained by means of adding, to a siliconematerial, such particles as silicon oxide, aluminium oxide, zirconiumoxide, titanium oxide, yttrium oxide, niobium oxide or the like, forexample.

Furthermore, the above-mentioned liquid medium may be further added witha known additive such as diffusing agent, filler, viscosity modifier andUV absorbing agent. These additives can be used either as a single oneor as a combination of two or more kinds in any combination and in anyratio.

[6-2. (Other) Configurations of Light Emitting Device]

There is no special limitation on the other configuration of the lightemitting device of the present invention, insofar as it comprises theabove-mentioned first luminous body and second luminous body. However,it usually comprises a frame on which the above-mentioned first luminousbody and second luminous body are located. The location is configured sothat the second luminous body is excited (namely, the first and secondphosphors are excited) by the light emitted from the first luminous bodyto emit light and the lights from the first luminous body and/or fromthe second luminous body are radiated to the outside. At this point, itis not always necessary for the first and second phosphors to becontained in the same layer. Each of different colored phosphors may becontained in the different layer from each other. For example, a layercontaining the second phosphor can be laminated on a layer containingthe first phosphor.

The light emitting device of the present invention may also utilize amember other than the above-mentioned excitation light source (the firstluminous body), the phosphor (the second luminous body) and a frame. Asthe example can be cited the aforementioned sealing material. Thesealing material can be used for, in addition to dispersing the phosphor(the second luminous body), adhering the excitation light source (thefirst luminous body), the phosphor (the second luminous body) and theframe to each other, in the light emitting device.

[6-3. Embodiment of Light Emitting Device]

The light emitting device of the present invention will be explained indetail below with reference to a concrete embodiment. However, it is tobe noted that the present invention is by no means restricted to thefollowing embodiment and any modifications can be added thereto insofaras they do not depart from the scope of the present invention.

FIG. 1 is a schematic perspective view illustrating the positionalrelationship between the first luminous body, which functions as theexcitation light source, and the second luminous body, constructed asthe phosphor-containing part containing a phosphor, in an example of thelight emitting device of the present invention. In FIG. 1, the numeral 1indicates a phosphor-containing part (second luminous body), the numeral2 indicates a surface emitting type GaN-based LD as an excitation lightsource (first luminous body), and the numeral 3 indicates a substrate.In order to configure them so that they are in contact with each other,the LD (2) and the phosphor-containing part (second luminous body) (1),prepared separately, may be made contact with each other in theirsurfaces by means of adhesive or the like, or otherwise, a layer of thephosphor-containing part (second luminous body) may be formed (molded)on the emission surface of the LD (2). With such configurations, the LD(2) and the phosphor-containing part (second luminous body) (1) can bekept contact with each other.

With such device configurations, light quantity loss, induced by aleakage of light emitted from the excitation light source (firstluminous body) and reflected on the layer surface of thephosphor-containing part (second luminous body) to outside, can beavoided, which makes possible enhancement in emission efficiency of theentire device.

FIG. 2( a) shows a typical example of a light emitting device generallycalled a sell type. It is a schematic sectional view illustrating anexample of the light emitting device comprising an excitation lightsource (first luminous body) and a phosphor-containing part (secondluminous body). In this light emitting device (4), the numeral 5,numeral 6, numeral 7, numeral 8, numeral 9 and numeral 10 indicate amount lead, inner lead, excitation light source (first luminous body),phosphor-containing resinous part, conductive wire and mold member,respectively.

FIG. 2( b) shows a typical example of a light emitting device generallycalled a surface-mount type. It is a schematic sectional viewillustrating an example of the light emitting device comprising anexcitation light source (first luminous body) and a phosphor-containingpart (second luminous body). In the Figure, the numeral 22, numeral 23,numeral 24, numeral 25 and numerals 26, 27 indicate an excitation lightsource (first luminous body), a phosphor-containing resinous part asphosphor-containing part (second luminous body), a frame, a conductivewire and electrodes, respectively.

[6-4. Use of Light Emitting Device]

There is no special limitation on the use of the light emitting deviceof the present invention, and therefore it can be used in various fieldswhere a usual light emitting device is used. However, owing to its widecolor reproduction range and high color rendering, it can be used as alight source of illuminating devices or displays particularlypreferably.

[6-4-1. Illuminating Device]

The application of the light emitting device of the present invention toan illuminating device can be carried out by incorporating a lightemitting device such as described earlier into a known illuminatingdevice as appropriate. A surface-emitting illuminating device (11),shown in FIG. 3, in which the aforementioned light emitting device (4)is incorporated, can be cited as the example.

FIG. 3 is a sectional view schematically illustrating an embodiment ofthe illuminating device of the present invention. As shown in this FIG.3, the surface-emitting illuminating device comprises a large number oflight emitting devices (13) (corresponding to the aforementioned lightemitting device (4)) on the bottom surface of a rectangular holding case(12), of which inner surfaces are made to be opaque ones such as whitesmooth surfaces, and a power supply, circuit or the like (not shown inthe figure) for driving the light emitting devices (13) outside theholding case. In addition, it comprises a milky-white diffusion plate(14), such as an acrylic plate, at the place corresponding to the coverpart of the holding case (12), for homogenizing the light emitted.

When the surface-emitting illuminating device (11) is driven by means ofapplying a voltage to the excitation light source (the first luminousbody) of the light emitting device (13), light is emitted from the lightsource and the aforementioned phosphor in the phosphor-containingresinous part, which serves as phosphor-containing part (the secondluminous body), absorbs a part of the emitted light and emits visiblelight. On the other hand, the blue light that is not absorbed in thephosphor is mixed with the visible light to form a light emission withhigh color rendering, and then the mixed light passes through thediffusion plate (14) to be radiated in the upward direction of thefigure. Consequently, an illumination light with a brightness that isuniform within the surface of the diffusion plate (14) of the holdingcase (12) can be obtained.

[6-4-2. Display]

When the light emitting device of the present invention is used as alight source in a display, there is no limitation on the concreteconfiguration of the display. However, it is preferable to be usedtogether with a color filter. For example, a color display, which is akind of display, utilizing a color liquid-crystal display element can beformed by combining the above-mentioned light emitting device asback-lighting, an optical shutter utilizing a liquid crystal, and acolor filter having red, green and blue picture elements.

The NTSC ratio of the color reproduction range of the light passedthrough the color filter is usually 60% or higher, preferably 80% orhigher, more preferably 90% or higher, still more preferably 100% orhigher, and usually 150% or lower.

The transmitted light amount from each color filter relative to thetransmitted light amount from the entire color filters (namely, lightutilization efficiency) is usually 20% or higher, preferably 25% orhigher, more preferably 28% or higher, and still more preferably 30% orhigher. The higher the utilization efficiency, the more preferable.However, since three kinds of filters red, green and blue are used, theyare usually 33% or lower.

Example

The present invention will be explained specifically below by referringto examples. However, the present invention is not limited to theexamples and any modifications can be added thereto insofar as they donot depart from the scope of the present invention.

I. Examples with Respect to Phosphor of Present Invention (I)

In what follows, Examples or the like with respect to the phosphor ofthe present invention (I) will be explained.

[Raw Materials]

As commercially available materials for a phosphor, lanthanum nitridepowder (manufactured by Kojundo Chemical Lab. Co., Ltd), silicon nitridepowder (Si₃N₄, manufactured by DENKI KAGAKU KOGYO KABUSHIKI KAISHA, meanparticle diameter of 0.5 μm, oxygen content of 0.93 weight %, α-typecontent of 92%), and cerium oxide powder (manufactured by Shin-EtsuChemical Co., Ltd.) were used. As another phosphor material, synthesizedCaSiN₂ powder was used.

[Measurement Methods]

[Emission Spectrum]

The emission spectra were measured by using a fluorescence measurementapparatus (manufactured by JASCO corporation) equipped with anexcitation light source of 150-W xenon lamp and a spectrum measurementapparatus of multichannel CCD detector, C7041 (manufactured by HamamatsuPhotonics K.K.). The lights from the excitation light source were passedthrough a grating monochromator with focal length of cm so as to isolatethe excitation lights of 460-nm or 465-nm wavelength, and the isolatedexcitation lights were radiated onto the phosphors via an optical fiber.The lights emitted from the phosphors by irradiation of the excitationlight were separated using a grating monochromator with focal length of25 cm, and the emission intensity of each wavelength of the lights wasmeasured using the spectrum measurement apparatus at the wavelengthrange of from 300 nm to 800 nm. Then, through a signal processing suchas sensitivity correction by a personal computer, the emission spectrawere obtained. The slit width of the receiving spectroscope wasspecified at 1 nm during the measurement.

[Full Width at Half Maximum of Emission Peak]

The full width at half maximum of each emission peak (hereinafter simplyreferred to as “the full width at half maximum” occasionally) wascalculated from the emission spectra obtained by the above-mentionedmethod.

[Color Coordinates]

The color coordinates of x, y colorimetric system (CIE 1931 colorimetricsystem) were calculated, as color coordinates x and y of the XYZcolorimetric system defined in JIS 28701, by a method in accordance withJIS Z8724 from the data of the emission spectra in the wavelength regionof from 420 nm to 800 nm obtained by the above-mentioned method.

[Method for Measuring Excitation Spectrum]

The excitation spectra were measured using a fluorescencespectrophotometer, F-4500 type, (manufactured by Hitachi, Ltd.) at aroom temperature.

[Internal Quantum Efficiency, External Quantum Efficiency, andAbsorption Efficiency]

The absorption efficiency α_(q), internal quantum efficiency η_(i), andexternal quantum efficiency η_(o) of the phosphor were determined by thefollowing procedure. First, the phosphor sample to be measured isstuffed up in a cell with its surface smoothed sufficiently to keep highmeasurement accuracy, and then it was set on an integrating sphere.

The integrating sphere was irradiated with light, from a light emissionsource (150-W Xe lamp) for exciting the phosphor, using an opticalfiber. The light from the aforementioned light emission source wasadjusted to be a monochromatic light having a wavelength of emissionpeak of 455 nm using a monochromator (grating monochromator) and thelike. Then the spectra of the emitted light (fluorescence) and thereflected light from the phosphor sample were measured using aspectrometer (MCPD7000, manufactured by Otsuka Electronics Co., Ltd.) byirradiating the phosphor sample to be measured with the abovemonochromatic excitation light. The light within the integrating spherewas guided to the spectrometer with an optical fiber.

Absorption efficiency α_(q) takes the value obtained through dividingN_(abs) by N, where N_(abs) is the number of photons of the excitationlight that is absorbed in the phosphor sample and N is the number of allthe photons in the excitation light.

First, the latter one, namely the total number N of all the photons inthe excitation light is proportional to the numerical value obtained bythe (formula a) below. Therefore, the reflection spectrum I_(ref)(λ) wasmeasured using a spectrometer for a reflection plate “Spectralon” withreflectance R of approx. 100% to excitation lights (actually withreflectance of 98% to the 450-nm excitation light) manufactured byLabsphere, by attaching it to the above-mentioned integrating sphere inthe same disposition as the phosphor sample and radiating the excitationlight thereon, and then the value of the (formula a) below wascalculated.

$\begin{matrix}\lbrack {{Mathematical}{\mspace{11mu}\;}{Formula}{\mspace{11mu}\;}4} \rbrack & \; \\{\frac{1}{R}{\int{{\lambda \cdot {I_{ref}(\lambda)}}{\mathbb{d}\lambda}}}} & ( {{formula}\mspace{14mu} a} )\end{matrix}$

The integration interval was set at from 410 nm to 480 nm with respectto the excitation wavelength of 455 nm.

The number N_(abs) of the photons in the excitation light absorbed inthe phosphor sample is proportional to the amount calculated in thefollowing (formula b).

$\begin{matrix}\lbrack {{Mathematical}{\mspace{11mu}\;}{Formula}{\mspace{11mu}\;}5} \rbrack & \; \\{{\frac{1}{R}{\int{{\lambda \cdot {I_{ref}(\lambda)}}{\mathbb{d}\lambda}}}} - {\int{{\lambda \cdot {I(\lambda)}}{\mathbb{d}\lambda}}}} & ( {{formula}\mspace{14mu} b} )\end{matrix}$

Therefore, the reflection spectrum 1(λ) was decided with the phosphorsample of which absorption efficiency α_(q) is intended to be determinedattached. The integration interval in (formula b) was set to be the sameas in (formula a). Since the actual measurement value of the spectrum isgenerally obtained as digital data which are divided by a certain finiteband width relating to λ, the integrations of (formula a) and (formulab) were calculated as finite sum based on the band width.

Then, the value of α_(q)=N_(abs)/N=(formula b)/(formula a) wascalculated.

Next, the internal quantum efficiency η_(i) was decided according to thefollowing procedure. The internal quantum efficiency η_(i) takes thevalue obtained through dividing N_(PL) by N_(abs), where N_(PL), is thenumber of photons originating from the fluorescence phenomenon andN_(abs) is the number of photons absorbed in the phosphor sample.

Here, N_(PL), is proportional to the amount calculated by the following(formula c). Therefore, the amount calculated by the following (formulac) was determined.[Mathematical Formula 6]∫λ·I(λ)dλ  (formula c)

The integration interval was set at from 481 nm to 800 nm with respectto the excitation wavelength of 455 nm.

Then, the internal quantum efficiency η_(i) was determined by thecalculation of η_(i)=(formula c)/(formula b).

Incidentally, the integration from spectra expressed by digital data wascarried out in the same way as when the absorption efficiency α_(q) wascalculated.

The external quantum efficiency η_(o) was then decided as a product ofthe absorption efficiency α_(q) and internal quantum efficiency η_(i),which were determined as above.

Example I-1

(Preparation of CaSiN₂ Powder)

First, CaSiN₂ powder was synthesized by a procedure described below.Calcium nitride powder (Ca₃N₂) and silicon nitride powder (Si₃N₄, meanparticle diameter of 0.5 μm, oxygen content of 0.93 weight %, α-typecontent of 92%) were weighed out at the weight ratio of 1:0.946 andmixed with a pestle and mortar for 10 min. Subsequently, the mixture wasfilled into a boron nitride crucible. The steps of weighing, mixing, andfilling of the powders were all performed within a glove box that cankeep its nitrogen atmosphere under 1 ppm or lower in moisture contentand oxygen content. The boron nitride crucible holding the materials wasplaced in an electric graphite resistance furnace. Then, a firing stepwas carried out as follows. First, the firing atmosphere was evacuatedwith a diffusion pump and then heated from room temperature to 800° C.at a rate of 20° C./min, followed by introducing nitrogen with a purityof 99.999 volume % at 800° C. until the pressure reached 0.92 MPa. Thetemperature was raised to 1600° C. at a rate of 20° C./min, maintainedat 1600° C. for hours, further raised to 1800° C. at. 20° C./min, andmaintained at 1800° C. for another 2 hours. After coarse milling of thefired product, it was pulverized with a silicon nitride sinter mortarand pestle, thereby obtaining a CaSiN₂ powder.

(Production of Phosphor)

Then, the CaSiN₂ powder, lanthanum nitride powder, cerium oxide powder,and silicon nitride powder were weighed out respectively at weights (g)described in Table I-1. Subsequently, the steps of mixing, filling,firing, and coarse milling were performed in the same way as thesynthesis of the CaSiN₂ powder (firing step), except that thetemperature program over 800° C. of the firing step was changed in sucha way that the temperature was raised to 2000° C. at a rate of 20°C./min and the temperature was maintained at 2000° C. for 2 hours. Aphosphor powder was thereby obtained.

Table I-1 shows the raw materials (namely, the phosphor precursors) andtheir charge weights. Table I-2 shows the charge molar ratios of theelements from the raw materials, letting the molar quantity of Si be 6.Table I-2 also shows the main-peak relative intensities of the powderX-ray diffraction patterns, which indicate to how much degree the phasesof LaSi₃N₅ and the intended Ca_(1.5x)La_(3−x)Si₆N₁₁ are generated in theresultant phosphor sample, and the luminescent characteristics of theemission spectra obtained when excited by respective wavelengths. As theradiation source for the powder X-ray diffraction pattern measurement,the CuKα line (1.54056 Å) was used.

From the Table I-2, it is evident that the phosphor sample offered asignificantly large full width at half maximum of the orange emissionpeak, 149 nm, when excited by the 460-nm-wavelength light of a blue LEDlight source.

Example I-2 to I-6 and Comparative Example I-1

The experiments were carried out in the same way as Example I-1 exceptthat the charge weights of the materials were changed as described inTable I-1 and the charge molar ratios of Ca, La, Ce, and Si were changedas described in Table I-2. Table I-2 also shows the main-peak relativeintensities of the powder X-ray diffraction patterns, which indicate tohow much degree the phases of LaSi₃N₅ and the intendedLa_(3−x−y)Ca_(1.5x+y)Si₆O_(y)N_(11−y) are generated in the resultantphosphor sample, and the luminescent characteristics of the emissionspectra obtained when excited by respective wavelengths. As theradiation source for the powder X-ray diffraction pattern measurement,the CuKα line (1.54056 Å) was used.

Table I-2 clearly shows that change in the charge ratio of Ca relativeto La varied the amount of intended La_(3−x−y)Ca_(1.5x+y)S₆O_(y)N_(11−y)phase produced. Therefore, it is evident that the orange phosphor of thepresent invention is a new substance actively relating to Ca, a bivalentelement, in addition to La, a trivalent element, among nitrides. Fromthe results of the above-mentioned experiments, it can be inferred thatthe desirable charge ratio of La:Ca is usually 2:1 or higher, preferably1.8:1 or higher, more preferably 1.5:1 or higher, and usually 1:2 orlower, preferably 1:1.8 or lower, more preferably 1:1.5 or lower. Inthis context, “high” means that the content of Ca is high.

From the Table I-2, it is evident that the orange phosphors offeredsignificantly large full width at half maximums of the orange emissionpeaks, 146 nm to 156 nm. Concerning Example I-6, accurate measurementfor the full width at half maximum could not be performed because itswavelength of emission peak was 566 nm and its spectrum was so wide thatit was overlapped partly with the excitation light spectrum.

Examples I-7 to I-12

The charge weights of the materials were changed as described in TableI-1 so that the amount of Ce, the activation element, varied while themolar ratios of Ca and (La+Ce) remained the same when letting the molarquantity of Si be 6. The experiments were carried out in the same way asExample I-1 except that the charge weights were changed. In everyExample, LaSi₃N₅:Ce was not at all produced, but intendedLa_(3−x−y)Ca_(1.5x+y)Si₆O_(y)N_(11−y) phase was only produced, as thephosphor. Thereby, orange phosphors that can be preferably used with ablue LED could be obtained. Table I-3 shows the emission intensities,luminous wavelengths, full width at half maximums, and color coordinatesof the orange emission peaks of the phosphors.

As shown in Table I-3, the orange emission intensity was the highestwhen the Ce molar ratio was 0.1. The emission spectra of the powders ofExample I-8, containing 0.1 molar ratio of Ce, a commercially availableY₃Al₅O₁₂:Ce phosphor (product number P46-Y3, manufactured by KaseiOptonics, Ltd.), and a LaSi₃N₅:Ce phosphor of Comparative Example I-1are shown in FIG. 4. From FIG. 4, it is evident that the phosphor ofExample I-8 offered a significantly wider full width at half maximum,156 nm, than that of Y₃Al₅O₁₂:Ce, 126 nm, and an emission spectrum ofwhich red wavelength region is sufficiently intensive, when excited by alight of blue LED wavelength. Accordingly, use of the phosphor ofExample I-8 in combination with a blue LED can create a warm white lightof which color rendering is remarkably good.

In addition, it is evident from Table I-3 that the other phosphors ofthe present invention (the phosphors of Examples I-1, I-7, I-9 to I-12)have also significantly wide full width at half maximums, 149 nm to 165nm.

FIG. 5 is a graph showing the powder X-ray diffraction pattern of thephosphor, which was washed with aqua regia, of Example I-8. As theradiation source for the powder X-ray diffraction pattern measurement,the CuKα line (1.54056 Å) was used. From FIG. 5, it is evident that theintended La_(3−x−y)Ca_(1.5x+y)Si₆O_(y)N_(11−y) phase was produced as asingle phase.

Furthermore, a Rietveld analysis of the result of the precise X-raydiffraction and an elemental analysis revealed that the chemicalcomposition of the phosphor of Example I-8 wasLa_(3−x−y−z)Ce_(z)Ca_(1.5x+y)Si₆O_(y)N_(11−y) (where, x=0.75, y=0.44,z=0.1).

Examples I-13, I-14, I-15, I-16

Examples I-13, I-14, I-15, and I-16 were performed in the same way asExamples I-1, I-8, I-11, and I-12 except that the firing temperature waschanged from 2000° C. to 1900° C. In every Example, LaSi₃N₅:Ce was notat all produced, but the intended La_(3−x−y)Ca_(1.5x+y)Si₆O_(y)N_(11−y)phase was only produced, as the phosphor. Thereby, orange phosphors thatcan be preferably used with a blue LED could be obtained. Table I-3shows the emission intensities and luminous wavelengths of the orangeemission peaks of the phosphors. As shown in table I-3, the orangeemission intensity was the highest when the Ce molar ratio was 0.49.

TABLE I-1 Example or Comparative Charge weight (g) of each materialExample CaSiN₂ LaN CeO₂ Si₃N₄ Example I-1 0.5567 0.654 0.013 0.4762Example I-2 0.5277 0.555 0.014 0.6035 Example I-3 0.3849 0.803 0.0120.4997 Example I-4 0.6116 0.477 0.014 0.5969 Example I-5 0.4195 0.6550.013 0.6119 Example I-6 0.2584 0.805 0.012 0.6245 Comparative 0.28170.657 0.013 0.7482 Example I-1 Example I-7 0.5536 0.651 0.022 0.4735Example I-8 0.5464 0.642 0.044 0.4674 Example I-9 0.5371 0.631 0.0720.4595 Example I-10 0.5259 0.618 0.106 0.4499 Example I-11 0.5152 0.6050.139 0.4407 Example I-12 0.495 0.582 0.200 0.4234 Example I-13 0.55670.654 0.013 0.4762 Example I-14 0.5464 0.642 0.044 0.4674 Example I-150.5152 0.605 0.139 0.4407 Example I-16 0.495 0.582 0.200 0.4234

TABLE I-2 Peak intensity ratio of X-ray diffraction of phase producedIntensity ratio of emission peaks Example or Peak at Peak at Orange peakwhen Blue peak when Comparative Charge molar ratio 2θ = 18.0° of 2θ =20.0° of excited by excited by Example Ca La Ce Si intended phaseLaSi₃N₅ phase 460 nm 340 nm Example I-1 2.2 1.6 0.028 6 100 0 100 0Example I-2 1.8 1.2 0.026 6 66 34 71 29 Example I-3 1.6 2.1 0.028 6 6436 100 0 Example I-4 2.0 1.0 0.026 6 45 55 52 48 Example I-5 1.5 1.50.026 6 39 61 65 35 Example I-6 1.0 2.0 0.026 6 26 74 43 57 Comparative0.9 1.4 0.025 6 0 100 0 100 Example I-1 Orange emission peak Blueemission peak when excited by 460 nm when excited by 340 nm Example orEmission Emission Full width at Color Color Emission EmissionComparative intensity wavelength half maximum coordinate coordinateintensity wavelength Example (a.u.) (nm) (nm) x y (a.u.) (nm) ExampleI-1 15.4 579 149 0.488 0.497 0 — Example I-2 10.5 588 155 0.497 0.4904.3 428 Example I-3 9.0 569 146 0.461 0.518 0 — Example I-4 5.3 590 1550.489 0.493 4.9 436 Example I-5 10.0 580 156 0.485 0.499 5.5 426 ExampleI-6 4.6 566 — 0.449 0.525 6.2 429 Comparative 0.0 — — — — 13 442 ExampleI-1

TABLE I-3 molar ratio of Orange emission peak when excited by 460 nmRealative intensity Ca_(1.8)La_((1.8−a)) Firing Emission Emission Fullwidth at Color Color of blue emission Ce_(a)Si₆(N,O)₁₁ temperature/intensity wavelength half maximum coordinate coordinate peak whenexcited Example Ce molar ratio a ° C. (a.u.) (nm) (nm) x y by 340 nmExample I-1 0.03 2000 15.4 579 149 0.488 0.497 0.0 Example I-7 0.05 200017.3 585 151 0.504 0.486 0.0 Example I-8 0.10 2000 19.6 591 156 0.5190.473 0.0 Example I-9 0.16 2000 15.6 596 156 0.528 0.465 0.0 ExampleI-10 0.25 2000 15.8 597 158 0.538 0.457 0.0 Example I-11 0.33 2000 15.7608 160 0.547 0.449 0.0 Example I-12 0.49 2000 11.7 611 165 0.552 0.4440.0 Example I-13 0.03 1900 16.4 578 152 0.488 0.497 0.0 Example I-140.10 1900 16.1 591 160 0.526 0.467 0.0 Example I-15 0.33 1900 17.8 611164 0.554 0.441 0.0 Example I-16 0.49 1900 19.4 613 165 0.559 0.437 0.0

Examples I-17 to I-24

The charge weights of the materials were changed as described in TableI-4, and the temperature program over 800° C. of the firing step waschanged in such a way that the temperature was raised from 800° C. to2000° C. at a rate of 22° C./min and the temperature was maintained at2000° C. for 5 min. Except for those points, experiments were performedin the same way as Example I-1, and phosphors were thereby obtained.

The luminescent characteristics of the resultant phosphor when excitedby a light of 460-nm wavelength were measured in the same way asdescribed earlier. FIG. 6 shows the measured emission spectra, and TableI-5 shows the luminescent characteristics including the emissionintensities, wavelength of emission peaks, full width at half maximums,and CIE color coordinates.

With respect to the phosphor of Example I-18, its excitation spectrumwas measured using a monitoring wavelength of 577 nm, and also, itsemission spectrum was measured using an excitation wavelength of 465 nm.FIG. 7( a) shows the excitation spectrum and 7(b) shows the emissionspectrum.

FIGS. 8( a) and 8(b) show the powder X-ray diffraction patterns,measured using the CuKα line (1.54056 Å), of the phosphors prepared inExamples I-17 and I-22, of which substitution rates x (namely, the valuex in the above-mentioned formula [I]) were such that x=0.5 and x=1.8, interms of the charge composition, respectively. Crystal indices astetragonal system are shown for each peak in FIG. 8( a) and FIG. 8( b).It is clear from FIGS. 8( a) and 8(b) that the intended phases could beobtained almost as a single phase and the La was substituted with 1.5times amount (in molar ratio) of Ca even when the substitution rate xwas as high as 1.8. We verified that, in all the phosphors of ExamplesI-17 to I-24, no LaSi₃N₅ phases were generated butLa_(3−x−y−z)Ce_(z)Ca_(1.5x+y)Si₆O_(y)N_(11−y) phases were generated asphosphors, as typified by FIG. 8( a) and FIG. 8( b).

In addition, the powder X-ray diffraction patterns were measured on thephosphors obtained in the above-mentioned Examples using the CuKα line(1.54056 Å). The actual measured values of 2θ of the respective peaks ofthe powder X-ray diffraction pattern, corresponding to differentsubstitution rates x of the La with 1.5 times amount (in molar ratio) ofCa (specifically, x=0.5 in the charge composition ratio of Example I-17,x=0.7 in the charge composition ratio of Example I-18, x=1.6 in thecharge composition ratio of Example I-21, x=1.8 in the chargecomposition ratio of Example I-22, and x=2.0 in the charge compositionratio of Example I-23), are shown in Table I-6. It is evident that, withincreasing substitution rates x, the value of 2θ changes significantly.

Table I-6 also shows calculated values obtained by fitting the actualmeasured values of 2θ of the respective peaks with the plane indices oftetragonal system. These calculated values were obtained from theequation below by the least square method. In the equation, the latticeconstants of a axis and c axis of tetragonal system are designated as aand c respectively, and the plane indices are designated as (hkl). Inthe equation, λ is the wavelength 1.54056 Å of the Kα line of Cu, usedas the X-ray source.2θ=2 sin⁻¹[0.5λ(h ² /a ² +k ² /a ² +l ² /c ²)^(0.5)]

As can be seen from Table I-6, the actual measured values and thecalculated values match within the limit of error. It is also evidentthat, as the substitution rate x changes, the powder X-ray diffractionpattern also changes. This is because the lattice constant of tetragonalsystem changes then.

Table I-7 shows changes in the lattice constant that were calculatedfrom the measurement results of the powder X-ray diffraction patterns.From the table, it is evident that, with increasing x values of 0.5,0.7, 1.6, 1.8, and 2.0, the lattice constant of a axis decreases and thelattice constant of c axis increases. The volume of the unit cell, whichcan be calculated as (the lattice constant of a axis)²×(the latticeconstant of c axis)², increases as the value x increases. This isprobably because the substitution for La³⁺ with Ca²⁺, which has a littlesmaller ionic radius, is not of 1:1 type, but of unique, 1.5:1 type.

Also in light of the emission spectra of the respective Examples shownin FIG. 6 and the data on the luminous wavelengths of the respectiveExamples shown in Table I-5, it is evident that a change in x valuevaried the lattice constant and accordingly the luminous wavelength wasshifted significantly to the longer wavelength side. Therefore, whenusing the phosphor of the present invention, it is very easy to controlthe color temperature of the white light synthesized by adjusting the xvalue.

In addition, the quantum efficiency measurements on the phosphor ofExample I-20 showed that it had an internal quantum efficiency of 47.3%,absorption efficiency of 83.2%, and external quantum efficiency of39.4%.

Furthermore, an elemental analysis with an oxygen-nitrogen analyzer andan ICP (inductively-coupled plasma) analyzer on the phosphor of ExampleI-22 showed that it has a crystal phase represented byLa_(3−y−z)Ce_(z)Ca_(1.5x+y)Si₆N_(11−y)O_(y) (where, x=1.14, y=0.53,z=0.1).

Example I-25

About 0.7 g of the phosphor powder produced in

Example I-17 was weighed out and fired again (secondary firing). Then,by a coarse milling of the fired product, a phosphor powder wasobtained.

The specific firing condition of the above-mentioned secondary firingwas the same as that of Example I-17 except that the temperature programover 800° C. was changed in such a way that the temperature was raisedfrom 800° C. to 1500° C. at a rate of 3° C./min and then maintained at1500° C. for 58.5 hours.

The luminescent characteristics of the resultant phosphor when excitedby a light of 460-nm wavelength were measured in the same way asdescribed earlier. The luminescent characteristics measured are shown inTable I-5. It is evident that the emission intensity was furtherincreased by carrying out the secondary firing, in comparison with thephosphor obtained in Example I-17.

Example I-26

An experiment was carried out in which the phosphor composition ofExample I-8 was changed in such a way that 0.59 mol of La wassubstituted with the same mol of Ca, and 0.59 mol of N was substitutedwith the same mol of O, by changing the charge weights of the materialsin accordance with Table I-4. Namely, an experiment was carried out inthe same way as Example I-8, except that the charge weights of thematerials were changed as described in Table I-4 and the temperatureprogram over 800° C. of the firing step was changed in such a way thatthe temperature was raised from 800° C. to 2000° C. at a rate of 22°C./min and the temperature was maintained at 2000° C. for 2 hours.

The luminescent characteristics of the resultant phosphor when excitedby a light of 460-nm wavelength were measured in the same way asdescribed earlier. The emission spectrum measured is shown in FIG. 9,and the luminescent characteristics are shown in Table I-5.

Example I-27

An experiment was carried out in the same way as Example I-26, exceptthat the phosphor composition of Example I-8 was changed in such a waythat 0.4 mol of Si was substituted with the same mol of Al, and 0.4 molof Ca was substituted with the same mol of La, by changing the chargeweights of the materials in accordance with Table I-4. A phosphor wasthereby obtained.

The luminescent characteristics of the resultant phosphor when excitedby a light of 460-nm wavelength were measured in the same way asdescribed earlier. The emission spectrum measured is shown in FIG. 9,and the luminescent characteristics are shown in Table I-5.

Example I-28

An experiment was carried out in the same way as Example I-26, exceptthat the phosphor composition of Example I-8 was changed in such a waythat 0.4 mol of Si was substituted with the same mol of Al, and 0.4 molof N was substituted with the same mol of O, by changing the chargeweights of the materials in accordance with Table I-4. A phosphor wasthereby obtained.

The luminescent characteristics of the resultant phosphor when excitedby a light of 460-nm wavelength were measured in the same way asdescribed earlier. The emission spectrum measured is shown in FIG. 9,and the luminescent characteristics are shown in Table I-5.

By comparing the results of Examples I-8, and I-26 to I-28, it is clearthat their wavelength of emission peaks and full width at half maximumswere different, as can be seen in FIG. 9. This indicates that the colorrendering and the luminescent color can be finely adjusted by changingthe amount of O (oxygen) or Al.

Example I-29

The phosphor of Example I-29 was obtained in the same way as ExampleI-14 except that the charge weights of the materials were changed asdescribed in Table I-4.

The luminescent characteristics of the resultant phosphor when excitedby a light of 460-nm wavelength were measured in the same way asdescribed earlier. The luminescent characteristics measured are shown inTable I-5. It was verified that the reproducibility could be obtainedwithin the experimental error.

Example I-30

An experiment was carried out in the same way as Example I-29 exceptthat the 10 mole percent of Ca was substituted with Mg by changing thecharge materials, and thereby a phosphor was obtained.

The luminescent characteristics of the resultant phosphor when excitedby a light of 460-nm wavelength were measured in the same way asdescribed earlier. The emission spectrum measured is shown in FIG. 10,and the luminescent characteristics are shown in Table I-5. It isevident that the emission intensity was enhanced by charging Mg materialin place of Ca material.

Example I-31

An experiment was carried out in the same way as Example I-29 exceptthat the 20 mole percent of Ca was substituted with Mg by changing thecharge materials, and thereby a phosphor was obtained.

The luminescent characteristics of the resultant phosphor when excitedby a light of 460-nm wavelength were measured in the same way asdescribed earlier. The emission spectrum measured is shown in FIG. 10,and the luminescent characteristics are shown in Table I-5. It isevident that the emission intensity was enhanced by charging Mg materialin place of Ca material.

Example I-32

An experiment was carried out in the same way as Example I-18 exceptthat the 20 mole percent of Ca was substituted with Ba by changing thecharge materials.

The luminescent characteristics of the resultant phosphor when excitedby a light of 460-nm wavelength were measured in the same way asdescribed earlier. The emission spectrum measured is shown in FIG. 10,and the luminescent characteristics are shown in Table I-5.

Example I-33 to I-35

An experiment was carried out in which the La was substituted with Gd(Example I-33), with Y (Example I-34), and with Lu (Example I-35), bychanging the charge weight of the La material in accordance with TableI-4. Namely, the experiment was carried out in the same way as ExampleI-18 except that 0.3 mol of La was substituted with 0.3 mol of Gd, Y, orLu and 0.3 mol of N was substituted with 0.3 mol of 0 by changing thecharge materials, and thereby a phosphor was obtained.

The luminescent characteristics of the resultant phosphor when excitedby a light of 460-nm wavelength were measured in the same way asdescribed earlier. The luminescent characteristics measured are shown inTable I-5.

Example I-36

An experiment was carried out in the same way as Example I-17 exceptthat the CaSiN₂ powder, one of the raw materials, was used without beingexposed to the air after synthesized but by being stored in a glove boxthat can keep its nitrogen atmosphere under 1 ppm or lower in moisturecontent and oxygen content, and thereby a phosphor was obtained.

The luminescent characteristics of the resultant phosphor when excitedby a light of 460-nm wavelength were measured in the same way asdescribed earlier. The luminescent characteristics measured are shown inTable I-5.

In addition, the powder X-ray diffraction pattern was measured on theresultant phosphor using the CuKα line (1.54056 Å). The powder X-raydiffraction pattern measured is shown in FIG. 8( c).

It is evident from Table I-5 that the emission intensity of the phosphorobtained in the present Example was enhanced in comparison with thephosphor of Example I-17. This indicates that it is desirable forenhanced luminescent characteristics of a phosphor to use a CaSiN₂powder containing as little oxygen and moisture as possible as a rawmaterial. It is also evident, from the resultant powder X-raydiffraction pattern, that the slightly-remaining impurity phasedisappeared.

In addition, the quantum efficiency measurements on the phosphor of thepresent Example showed that it had an internal quantum efficiency of46.5%, absorption efficiency of 80.3%, and external quantum efficiencyof 37.3%.

Example I-37

An experiment was carried out in the same way as Example I-25 except forthe points described below, and thereby a phosphor was obtained. Namely,the firing temperature program over 800° C. of the secondary firing ofExample I-25 was changed in such a way that the temperature was raisedfrom 800° C. to 1200° C. at a rate of 3° C./min, then from 1200° C. to1500° C. at a rate of 15° C./min, and then maintained at 1500° C. for 6hours. In addition, the CaSiN₂ powder was used without being exposed tothe air after synthesized but by being stored in a glove box that hasthe same properties as that of Example I-36.

The luminescent characteristics of the resultant phosphor when excitedby a light of 460-nm wavelength were measured in the same way asdescribed earlier. The luminescent characteristics measured are shown inTable I-5. It is evident from the result that the emission intensity wasfurther increased by carrying out the secondary firing on the phosphorobtained in Example I-17.

In addition, the quantum efficiency measurements on the phosphor of thepresent Example showed that it had an internal quantum efficiency of50.5%, absorption efficiency of 86.3%, and external quantum efficiencyof 43.8%.

Example I-38

An experiment was carried out in the same way as Example I-37 exceptthat the phosphor powder obtained in Example I-17 was fired inaccordance with the secondary firing step of Example I-37 using a fluxof CaF₂ of 0.5 weight % of the phosphor powder. Thereby, a phosphor wasobtained.

The luminescent characteristics of the resultant phosphor when excitedby a light of 460-nm wavelength were measured in the same way asdescribed earlier. The luminescent characteristics measured are shown inTable I-5.

Example I-39

A white light emitting device was produced by using the phosphor ofExample I-38, of which charge composition wasCa_(0.75)La_(2.4)Ce_(0.1)Si₆N₁₁, and a blue-light emitting GaN-based LEDchip (460EZ, manufactured by Cree, Inc.) in combination.

In order to disperse and seal the above-mentioned phosphor, a siliconeresin sealant (SCR-1011, manufactured by Shin-Etsu Chemical Co., Ltd.)and a dispersant (QS-30, manufactured by TOKUYAMA Corp.) were used. Theweight ratio of the phosphor powder of the ExampleI-38:sealant:dispersant was set at 4.0:97.0:3.0. After heating themixture of them at 70° C. for 1 hour, it was hardened by an additionalheating at 150° C. for 5 hours, thereby a phosphor-containing part wasformed. A surface-mount white light emitting device was then producedusing it.

The emission spectrum of the obtained light emitting device is shown inFIG. 11, and its spectral characteristics are shown in Table I-8. Thegeneral color rendering index of the obtained light emitting device was83. By bringing the color coordinate x close to 0.45 and the colorcoordinate y to 0.41, the general color rendering index will probably befurther improved.

TABLE I-4 Charge weight (g) of each material Rare earth element sourceCeO₂ LaN Si₃N₄ CaSiN₂ other than La Al₂O₃ La₂O₃ AlN MgSiN₂ Ba₃N₂ ExampleI-17 0.041 0.933 0.599 0.176 — — — — — — Example I-18 0.042 0.878 0.5780.252 — — — — — — Example I-19 0.042 0.813 0.506 0.390 — — — — — —Example I-20 0.045 0.661 0.481 0.562 — — — — — — Example I-21 0.0470.595 0.467 0.641 — — — — — — Example I-22 0.048 0.523 0.440 0.740 — — —— — — Example I-23 0.049 0.447 0.410 0.843 — — — — — — Example I-240.040 0.986 0.620 0.103 — — — — — — Example I-25 0.041 0.933 0.599 0.176— — — — — — Example I-26 0.051 — 0.408 0.921 — — 0.320 — — — ExampleI-27 0.040 0.823 0.426 0.348 — — — 0.064 — — Example I-28 0.044 0.6420.387 0.546 — 0.058 — 0.023 — — Example I-29 0.104 1.511 1.100 1.286 — —— — — — Example I-30 0.104 1.519 1.106 1.163 — — — — 0.108 — ExampleI-31 0.105 1.527 1.112 1.039 — — — — 0.217 — Example I-32 0.041 0.8530.585 0.196 — — — — — 0.075 Example I-33 0.040 0.733 0.555 0.242 0.130of Gd₂O₃ — — — — — Example I-34 0.042 0.755 0.571 0.249 0.084 of Y₂O₃ —— — — — Example I-35 0.040 0.727 0.550 0.240 0.142 of Lu₂O₃ — — — — —Example I-36 0.094 2.133 1.370 0.403 — — — — — — Example I-37 0.0942.133 1.370 0.403 — — — — — — Example I-38 0.041 0.931 0.598 0.176 — — —— — —

TABLE I-5 Firing condition Pressure Firing temperature and Firingtemperature and Example Charge composition Atmosphere (MPa) time(primary firing) time (secondary firing) Example I-17Ca_(0.75)La_(2.4)Ce_(0.1)Si₆N₁₁ N₂ 0.92 2000° C., 0.08 h none ExampleI-18 Ca_(1.05)La_(2.2)Ce_(0.1)Si₆N₁₁ N₂ 0.92 2000° C., 0.08 h noneExample I-19 Ca_(1.35)La_(2.0)Ce_(0.1)Si₆N₁₁ N₂ 0.92 2000° C., 0.08 hnone Example I-20 Ca_(2.17)La_(1.45)Ce_(0.1)Si₆N₁₁ N₂ 0.92 2000° C.,0.08 h none Example I-21 Ca_(2.4)La_(1.3)Ce_(0.1)Si₆N₁₁ N₂ 0.92 2000°C., 0.08 h none Example I-22 Ca_(2.7)La_(1.8)Ce_(0.1)Si₆N₁₁ N₂ 0.922000° C., 0.08 h none Example I-23 Ca_(3.0)La_(0.9)Ce_(0.1)Si₆N₁₁ N₂0.92 2000° C., 0.08 h none Example I-24 Ca_(0.45)La_(2.6)Ce_(0.1)Si₆N₁₁N₂ 0.92 2000° C., 0.08 h none Example I-25Ca_(0.75)La_(2.4)Ce_(0.1)Si₆N₁₁ N₂ 0.92 2000° C., 0.08 h 1500° C., 58.5h Example I-26 Ca_(2.7)La_(0.9)Ce_(0.1)Si₆N_(10.4)O_(0.6) N₂ 0.92 2000°C., 2 h none Example I-27 Ca_(1.7)La_(1.9)Ce_(0.1)Si_(5.6)Al_(0.4)N₁₁ N₂0.92 2000° C., 2 h none Example I-28Ca_(2.1)La_(1.5)Ce_(0.1)Si_(5.6)Al_(0.4)N_(10.6)O_(0.4) N₂ 0.92 2000°C., 2 h none Example I-29 Ca_(2.1)La_(1.5)Ce_(0.1)Si₆N₁₁ N₂ 0.92 1900°C., 2 h none Example I-30 Ca_(1.9)Mg_(0.2)La_(1.5)Ce_(0.1)Si₆N₁₁ N₂ 0.921900° C., 2 h none Example I-31 Ca_(1.7)Mg_(0.4)La_(1.5)Ce_(0.1)Si₆N₁₁N₂ 0.92 1900° C., 2 h none Example I-32Ba_(0.3)Ca_(0.75)La_(2.2)Ce_(0.1)Si₆N₁₁ N₂ 0.92 2000° C., 0.08 h noneExample I-33 Ca_(1.1)La_(1.9)Gd_(0.3)Ce_(0.1)Si₆N₁₁ N₂ 0.92 2000° C.,0.08 h none Example I-34 Ca_(1.1)La_(1.9)Y_(0.3)Ce_(0.1)Si₆N₁₁ N₂ 0.922000° C., 0.08 h none Example I-35Ca_(1.1)La_(1.9)Lu_(0.3)Ce_(0.1)Si₆N₁₁ N₂ 0.92 2000° C., 0.08 h noneExample I-36 Ca_(0.75)La_(2.4)Ce_(0.1)Si₆N₁₁ N₂ 0.92 2000° C., 0.08 hnone Example I-37 Ca_(0.75)La_(2.4)Ce_(0.1)Si₆N₁₁ N₂ 0.92 2000° C., 0.08h 1500° C., 6 h Example I-38 Ca_(0.75)La_(2.4)Ce_(0.1)Si₆N₁₁ N₂ 0.922000° C., 0.08 h 1500° C., 6 h and 0.5 weight % of CaF₂ Orange emissionpeak when excited by 460 nm Emission Emission Full width at intensitywavelength half maximum CIE Color coordinate Example (a.u.) (nm) (nm) xy Example I-17 18.0 571 142 0.461 0.512 Example I-18 21.3 577 148 0.4760.502 Example I-19 20.4 586 149 0.499 0.483 Example I-20 18.2 593 1530.511 0.472 Example I-21 16.9 596 156 0.517 0.468 Example I-22 15.5 598159 0.516 0.468 Example I-23 11.2 608 159 0.525 0.458 Example I-24 9.5566 137 0.448 0.517 Example I-25 25.1 579 129 0.478 0.507 Example I-2611.3 599 163 0.524 0.464 Example I-27 11.5 579 151 0.487 0.497 ExampleI-28 9.7 583 153 0.489 0.493 Example I-29 17.1 595 158 0.518 0.472Example I-30 17.5 595 158 0.520 0.471 Example I-31 19.9 595 155 0.5190.472 Example I-32 20.9 577 143 0.477 0.505 Example I-33 17.7 579 1490.484 0.500 Example I-34 16.3 579 149 0.482 0.502 Example I-35 8.9 578151 0.471 0.507 Example I-36 21.6 571 138 0.464 0.513 Example I-37 26.3572 135 0.465 0.514 Example I-38 25.5 568 138 0.459 0.517

TABLE I-6 2θ of phosphors of which La substitution rate is x x = 0.5 x =0.7 x = 1.6 x = 1.8 x = 2.0 Actual Actual Actual Actual Actual Planemeasured Calculated measured Calculated measured Calculated measuredCalculated measured Calculated indices hkl value value value value valuevalue value value value value 110 12.332 12.326 12.351 12.343 12.36312.392 12.347 12.380 12.356 12.397 001 18.207 18.204 18.154 18.15317.965 17.964 17.962 17.968 17.912 17.927 220 24.792 24.798 24.82724.833 24.915 24.931 24.891 24.907 24.924 24.943 211 26.823 26.83326.804 26.819 26.749 26.746 26.737 26.735 26.739 26.728 310 27.77027.780 27.809 27.819 27.925 27.930 27.895 27.903 27.934 27.944 22130.916 30.936 30.916 30.933 30.905 30.900 30.895 30.883 30.900 30.888311 33.397 33.416 33.402 33.420 33.417 33.408 33.401 33.387 33.40933.399 410 36.462 36.480 36.515 36.533 36.698 36.680 — 36.644 36.90036.698 002 36.852 36.889 36.750 36.783 36.387 36.389 36.411 36.39836.346 36.313 420 39.673 39.692 39.731 39.750 39.919 39.911 39.88339.872 39.945 39.931 411 41.041 41.061 41.064 41.084 41.136 41.12941.130 41.098 41.148 41.128

TABLE I-7 Lattice constants of tetragonal system calculated x value andCa molar ratio from XRD patterns of Ca_(1.5x)La_(2.9-x)Ce_(0.1)Si₆N₁₁Lattice Lattice Ca molar constant constant Example x value ratio 1.5x ofa axis of c axis Example I-17 0.5 0.75 10.156 4.873 Example I-18 0.71.05 10.141 4.887 Example I-21 1.6 2.4 10.102 4.938 Example I-22 1.8 2.710.112 4.937 Example I-23 2 3 10.097 4.948

TABLE I-8 Charge composition Emission characteristics (composition ofColor Color General color synthesized substance) coordinate x coordinatey rendering index Example I-39 Ca_(0.75)La_(2.4)Ce_(0.1)Si₆N₁₁ 0.3280.313 83 (x = 0.5)II. Examples with Respect to Phosphor of Present Invention (II)

In what follows, Examples or the like with respect to the phosphor ofthe present invention (II) will be explained.

[Raw Material Reagents]

The same commercially available raw materials were used as those used inthe section “I. Examples with respect to phosphor of present invention(I)” for producing the phosphors.

[Measurement Methods]

[Emission Spectrum]

The emission spectra were measured in the same way as those described inthe section “I. Examples with respect to phosphor of present invention(I)”.

[Full Width at Half Maximum of Emission Peak]

The full width at half maximums of the emission peaks were calculatedfrom the emission spectra obtained in the above-mentioned method.

[Color Coordinates]

The color coordinates of x, y colorimetric system (CIE 1931 colorimetricsystem) were measured in the same way as those described in the section“I. Examples with respect to phosphor of present invention (I)”.

[Method for Measuring Excitation Spectrum]

The excitation spectra were measured in the same way as those describedin the section “I. Examples with respect to phosphor of presentinvention (I)”.

[Measurement of Temperature Characteristics]

The temperature characteristics were examined as follows, for example,using an emission spectrum measurement device of multi-channel spectrumanalyzer, MCPD7000, manufactured by Otsuka Electronics Co., Ltd., abrightness measurement apparatus of the luminance colorimeter BMSA, astage equipped with a cooling mechanism using a peltiert device and aheating mechanism using a heater, and a light source device equippedwith a 150-W xenon lamp.

A cell holding the phosphor sample was put on the stage, and thetemperature was changed stepwise at 20° C., 25° C., 60° C., 100° C.,135° C., and 175° C. The surface temperatures of the phosphor weremeasured, and subsequently, the emission spectra were measured byexciting the phosphor with a light from the light source havingwavelength of 455 nm, which was separated using a diffraction grating.Then the emission peak intensities were decided from the measuredemission spectra. At this point, as the measurement values of thesurface temperatures of the phosphor on the side irradiated with theexcitation light, were used values corrected by the temperature valuesmeasured with a radiation thermometer and a thermocouple.

A corrected temperature—emission intensity curve at around 20° C. toaround 175° C. was plotted from the obtained emission-peak intensities.From the corrected temperature—emission intensity curve, I(130) andI(25), the values of the emission intensities at 130° C. and 25° C.respectively, were read out and then the temperature characteristicsvalue was calculated as I(130)/I(25). Actually, the I(130) and I(25)were not very different from the emission intensities at 130° C. and 25°C. that were not yet corrected.

[Internal Quantum Efficiency, External Quantum Efficiency, andAbsorption Efficiency]

The absorption efficiencies α_(q), internal quantum efficiencies η_(i),and external quantum efficiencies η_(o) of the phosphors were measuredin the same way as those described in the section “I. Examples withrespect to phosphor of present invention (I)”.

Example II-1

(Production of Alloy for Phosphor Precursor)

The material metals, Ce, La, and Si, (all of them were elemental metals)were weighed out so that the metal elements composition ratio becameCe:La:Si=0.1:2.9:6 (in molar ratio) and the total amount of them became2 g and mixed lightly, in a glove box of which atmosphere is a highpurity nitrogen with oxygen concentration of smaller than 1 ppm andwater vapor concentration of smaller than 1 ppm. The obtained mixture ofthe material metals was transferred into an arc melting furnace(ACM-CO1P, manufactured by DIAVAC LIMITED), and argon was introducedinto the furnace after air was evacuated from the furnace to 1×10⁻² Pa.Then, the material metals were melted in the argon atmosphere by passinga current of about 100 mA. After verifying that the melted metals wererotated sufficiently by an electromagnetic induction, the current wasstopped to be passed, and the melted product was solidified by naturalcooling. Thereby, an alloy for phosphor precursor with metal elementcomposition ratio of Ce:La:Si=0.1:2.9:6 (in molar ratio) was obtained.It was verified that the obtained alloy for phosphor precursor had auniform composition of the above-mentioned ratio using a scanningelectron microscope equipped with an energy dispersive X-rayspectrometer (namely, SEM-EDX), EX-250 manufactured by HORIBA, Ltd.

The alloy for phosphor precursor was pulverized in the same glove box asthe one described above using an alumina mortar and a nylon mesh sieveso as to be alloy powders having a particle diameter of 37 μm orsmaller, which was used as the material for a nitriding treatment.

(Secondary Nitriding Process)

(Primary Firing)

2 g of the obtained alloy powder was filled into a boron nitridecrucible (inner diameter of 20 mm) and the crucible was placed in a hotisostatic pressing instrument (HIP). After the air was evacuated fromthe instrument to 5×10⁻¹ Pa, nitrogen was filled into it until thepressure reached 11 MPa. Subsequently, the furnace temperature wasraised to 1050° C. at a temperature rising rate of 15° C./min. Afterverifying that the internal pressure reached 25 MPa, the furnacetemperature was raised from 1050° C. to 1205° C. at a rate of 3° C./minuntil the internal pressure reached 27 MPa. After that, the furnacetemperature was maintained at 1205° C. for 30 min, and then the pressurewas raised at a rate of 3° C./min. When the furnace temperature reached1750° C. and the internal pressure reached 33 MPa, cooling was startedand thus the nitriding treatment was ended.

The obtained nitride powder (nitrogen-containing alloy) was pulverizedin the same glove box as described above using an alumina mortar and anylon mesh sieve so as to be powders having a particle diameter of 37 μmor smaller, which was used as the material (primary fired product) forthe secondary firing described below.

(Secondary Firing)

About 1 g of the obtained nitrogen-containing alloy (namely, the primaryfired product) was filled into a boron nitride crucible (inner diameterof 20 mm) and the crucible was placed in a hot isostatic pressinginstrument (HIP). After the air was evacuated from the instrument to5×10⁻¹ Pa, nitrogen was filled into it until the pressure reached 25MPa. Subsequently, the furnace temperature was raised to 1300° C. at atemperature rising rate of 15° C./min. Then, the furnace temperature wasraised from 1300° C. to 2000° C. at a rate of 10° C./min until theinternal pressure reached 90 MPa. After the furnace temperature wasmaintained at 2000° C. for 3 hours, cooling was started and thus thefiring was ended.

The obtained fired product was pulverized in the same glove box asdescribed above using an alumina mortar, and thereby a phosphor wasobtained.

(Measurement of Luminescent Characteristics)

The luminescent characteristics of the resultant phosphor were examinedin a manner described earlier. FIG. 12 shows the measured emissionspectrum, and Table II-3 shows the luminescent characteristics includingthe emission intensity, wavelength of emission peak, full width at halfmaximum, and CIE color coordinates.

From FIG. 12, it is evident that the phosphor, La₃Si₆N₁₁:Ce, of thepresent Example, which was produced using an alloy as the material, havetwo emission peaks in its emission spectrum and the peak on shorterwavelength side is significantly higher than the peak at a wavelengthlonger than the shorter wavelength by 45 nm.

In addition, the value I(B)/I(A), which represents the ratio of (thepeak height on longer wavelength side)/(the peak height on shorterwavelength side), of the emission spectrum measured in the presentExample was as small as 0.852.

Since the phosphor, La₃Si₆N₁₁:Ce, of the present Example has theabove-mentioned emission spectrum, it is characterized by its yellowgreen luminescent color.

Example II-2

(Production of Alloy for Phosphor Precursor)

An alloy powder was prepared in the same condition as described in thesection “(Production of alloy for phosphor precursor)” of Example II-1.The steps of weighing and filling of the powder were all performedwithin a glove box that can keep its nitrogen atmosphere under 1 ppm orlower in moisture content and oxygen content, in the same way as ExampleII-1.

(Secondary Nitriding Process)

(Primary Firing)

About 0.7 g of the alloy powder was filled into a boron nitridecrucible, and it was placed in an electric graphite resistance furnace.Then, a firing was carried out as follows. Namely, the firing atmospherewas first evacuated with a turbo molecular pump and then the temperaturewas raised from room temperature to 800° C. at a rate of 20° C./min,followed by introducing nitrogen with a purity of 99.999 volume % at800° C. until the pressure reached 0.92 MPa. The temperature was thenraised to 1500° C. at a rate of 3° C./min and maintained at 1500° C. for58.5 hours. Thereby, the primary firing was carried out. By pulverizingthe resultant fired product in the same glove box as described above, apowder (primary fired product) was obtained.

(Secondary Firing)

The primary fired product was subjected to a secondary nitriding in acondition described below. Namely, the phosphor of the present Examplewas produced in the same condition as the above-mentioned primaryfiring, except that the temperature program over 800° C. of theabove-mentioned primary firing was changed in such a way that thetemperature was raised from 800° C. to 1500° C. at a rate of 1.5° C./minand maintained at 1500° C. for 3 hours, and then raised from 1500° C. to1750° C. at a rate of 15° C./min and maintained at 1750° C. for 7 hours.

(Measurement of Luminescent Characteristics)

The luminescent characteristics of the resultant phosphor were examinedin a manner described earlier. FIG. 12 shows the measured emissionspectrum, and Table II-3 shows the luminescent characteristics.

In addition, the value I(B)/I(A), which represents the ratio of (thepeak height on longer wavelength side)/(the peak height on shorterwavelength side), of the emission spectrum measured in the presentExample was as small as 0.816.

The luminescent color of the phosphor obtained in the present Examplewas green.

Furthermore, the temperature characteristics I(130)/I(25) of thephosphor obtained in the present Example was 74%.

In addition, the powder X-ray diffraction pattern was measured on thephosphor obtained in the present Example using the CuKα line (1.54184Å). By comparing the result of the phosphor of the present Example,prepared using an alloy as the phosphor material, with that of thephosphor of Reference Example II-1 (described later), prepared withoutusing an alloy as the phosphor material, it is evident that in thephosphor of the present Example there is extremely less impurity phasesand a crystal structure of La₃Si₆N₁₁ can be produced as a single phase.Furthermore, in the phosphor of the present Example, the ratio of thepeak intensity of the maximum peak (it indicates the peak of an impurityphase), in the 2θ range of 21° to 24°, to that of the 001 plane of theintended phase was as small as 0.027.

Example II-3

The phosphor of the present Example was produced in the same conditionas the above-mentioned Example II-2, except that the temperature programover 800° C. of the secondary firing of Example II-2 was changed in sucha way that the temperature was raised from 800° C. to 1500° C. at a rateof 0.27° C./min and maintained at 1500° C. for 58.5 hours, and thenraised from 1500° C. to 1750° C. at a rate of 15° C./min and maintainedat 1750° C. for 39 hours.

The luminescent characteristics of the resultant phosphor were examinedin a manner described earlier. FIG. 12 shows the measured emissionspectrum, and Table II-3 shows the luminescent characteristics.

In addition, the value I(B)/I(A), which represents the ratio of (thepeak height on longer wavelength side)/(the peak height on shorterwavelength side), of the emission spectrum measured in the presentExample was as small as 0.845.

The luminescent color of the phosphor obtained in the present Examplewas green.

Furthermore, the temperature characteristics I(130)/I(25) of thephosphor obtained in the present Example was 68%.

In addition, the quantum efficiency measurements on the phosphor of thepresent Example showed that it had an internal quantum efficiency of53.4%, absorption efficiency of 82.0%, and external quantum efficiencyof 43.8%.

In addition, the powder X-ray diffraction pattern was measured on thephosphor obtained in the present Example using the CuKα line (1.54184Å). The result is shown in FIG. 13. Crystal indices as tetragonal systemare shown for each peak of the powder X-ray diffraction pattern in FIG.13. By comparing the result of the phosphor of the present Example,prepared using an alloy as the phosphor material, with that of thephosphor of Reference Example II-1 (described later), prepared withoutusing an alloy as the phosphor material, it is evident that in thephosphor of the present Example there is extremely less impurity phasesand a crystal structure of La₃Si₆N₁₁ can be produced as a single phase.Furthermore, in the phosphor of the present Example, the ratio (namely,the peak intensity ratio I) of the peak intensity of the maximum peak(it indicates the peak of an impurity phase) that exists in the 2θ rangeof 21° to 24° to the peak intensity of the 001 plane of the intendedphase that exists in the 2θ range of 17° to 20° was as small as 0.027.

Moreover, from the emission spectra of Examples II-1 to II-3, it isevident that the phosphor that contains no A element such as Ca and isprepared using an alloy as the phosphor material shows a luminescentcolor of yellow green.

Example II-4

(Preparation of CaSiN₂, a Phosphor Material)

First, CaSiN₂ powder was synthesized by a procedure described below.Calcium nitride powder (Ca₃N₂) and silicon nitride powder were weighedout at the weight ratio of 1:0.946 and mixed with a pestle and mortarfor 10 min. Subsequently, the mixture was filled into a boron nitridecrucible. The steps of weighing, mixing, and filling of the powders wereall performed within a glove box that can keep its nitrogen atmosphereunder 1 ppm or lower in moisture content and oxygen content. The boronnitride crucible holding the materials was placed in an electricgraphite resistance furnace. Then, a firing step was carried out asfollows. Namely, the firing atmosphere was first evacuated with adiffusion pump and then heated from room temperature to 800° C. at arate of 20° C./min, followed by introducing nitrogen with a purity of99.999 volume % at 800° C. until the pressure reached 0.92 MPa. Thetemperature was then raised to 1750° C. at a rate of 15° C./min, andthen maintained at 1750° C. for 2 hours. Thereby, the firing step wascarried out. By a coarse milling of the fired product in the same glovebox, a CaSiN₂ powder, one of the raw materials, was obtained.

(Production of Alloy for Phosphor Precursor)

An La₄CeSi₁₀ alloy (alloy for phosphor precursor) powder of which metalelements composition ratio was such that Ce:La:Si=1:4:10 (in molarratio) was produced in the same way as Example II-1, except that themetal elements composition ratio of each material metal weighed out,described in the section “(Production of alloy for phosphor precursor)”of Example II-1, was changed so that Ce:La:Si=1:4:10 (in molar ratio).

(Secondary Nitriding Process)

Then, the La₄CeSi₁₀ alloy powder obtained as above, lanthanum nitridepowder, silicon nitride powder, and CaSiN₂ powder, were weighed out andmixed in the same glove box as that of Example II-1. At that time, thenumbers of moles of Ce in the La₄CeSi₁₀ alloy powder, La in thelanthanum nitride powder, Ca in the CaSiN₂ powder, and Si in the siliconnitride powder plus the La₄CeSi₁₀ alloy powder were specified so thatthey were proportional to the respective numbers of moles of Ce, La, Ca,and Si of the charge composition in Table II-1.

About 0.7 g of the obtained mixture was filled into a boron nitridecrucible, and the boron nitride crucible was placed in an electricgraphite resistance furnace. The firing atmosphere was first evacuatedwith a turbo molecular pump and then the temperature was raised fromroom temperature to 800° C. at a rate of 20° C./min, followed byintroducing nitrogen with a purity of 99.999 volume % at 800° C. untilthe pressure reached 0.92 MPa. The temperature was raised to 1580° C. ata rate of 3° C./min, maintained at 1580° C. for 57 hours, further raisedfrom 1580° C. to 2000° C. at a rate of 22° C./min, and then maintainedat 2000° C. for 5 min. Thereby, the firing was carried out. The obtainedfired product was pulverized in the same glove box as described aboveusing an alumina mortar, and thereby the phosphor powder of the presentExample was obtained.

(Measurement of Luminescent Characteristics)

The luminescent characteristics of the resultant phosphor were examinedin a manner described earlier. FIG. 14 shows the measured emissionspectrum, and Table II-3 shows the luminescent characteristics.

The phosphor of the present Example shows a high emission intensity andhas an emission peak shifted to longer wavelengths than those of thephosphors of Examples II-1 to II-3, which contained no A element such asCa. In addition, since it has a large full width at half maximum of 140nm, it is evident that it is a yellow phosphor that can contribute toenhancement of the color rendering.

In addition, the powder X-ray diffraction pattern was measured on thephosphor obtained in the present Example using the CuKα line (1.54184Å). The result is shown in FIG. 13. From FIG. 13, it is evident that asingle phase of tetragonal system P4bm or its analogous structurecontaining extremely little impurity phases could be produced by usingan alloy as the phosphor material. Furthermore, in the phosphor of thepresent Example, the ratio (namely, the peak intensity ratio I) of thepeak intensity of the maximum peak (it indicates the peak of an impurityphase) that exists in the 2θ range of 21° to 24° to the peak intensityof the 001 plane of the intended phase that exists in the 2θ range of17° to 20° was as small as 0.028.

An analysis performed on the phosphor obtained in the present Exampleusing an oxygen-nitrogen analyzer showed that the molar ratio(corresponding to y+w1) of O (oxygen) in the above-mentioned formula[II] was 0.24 and the molar ratio (corresponding to 11−y−w1) of N(nitrogen) in the above-mentioned formula [II] was 11.76.

Example II-5

The phosphor powder (primary fired product) obtained in Example II-4 wassubjected to a secondary firing in the condition described below.

The phosphor of the present Example was prepared by the same procedureas the section of (secondary nitriding process) of Example II-4, exceptthat the phosphor material was changed to the phosphor powder of ExampleII-4 and the temperature program over 800° C. was changed in such a waythat the temperature was raised to 1200° C. at a rate of 20° C./min,further raised to 1580° C. at a rate of 13° C./min, and maintained at1580° C. for 6 hours.

The luminescent characteristics of the resultant phosphor were examinedin a manner described earlier. FIG. 14 shows the measured emissionspectrum, and Table II-3 shows the luminescent characteristics. It isevident from FIG. 14 that performing a refiring can enhance the emissionintensity.

Examples II-6 to II-8

The phosphor powders of the Examples II-8, II-7, and II-6 were preparedby the same procedure as the section of (secondary nitriding process) ofExample II-4, except that the phosphor material used was the phosphorpowder of Example II-4 added with, respectively, 0.45 weight %, 0.9weight %, and 1.36 weight % of MgF₂ and mixed in the Example II-5.

The luminescent characteristics of the resultant phosphor were examinedin a manner described earlier. FIG. 14 shows the measured emissionspectrum, and Table II-3 shows the luminescent characteristics. It isevident that performing a nitriding in the presence of appropriateamount of flux MgF₂ can enhance the emission intensity.

Examples II-9, II-10

About 0.7 g of the phosphor powder (primary fired product) obtained inExample II-4 (Example II-9) and the phosphor powder (secondary firedproduct) obtained in Example II-6 (Example II-10) were weighed outrespectively. These were filled into a boron nitride crucible separatelyand placed in an electric furnace with a molybdenum heater. Afterevacuating the chamber to about 8 MPa, a nitrogen gas containinghydrogen (hydrogen:nitrogen=4:96 (in volume ratio)) was introducedtherein until the pressure reached normal pressure. With a nitrogen gascontaining 4% of hydrogen flowing at 0.5 L/min, the temperature wasraised to 1400° C. at a temperature rising rate of 5° C./min, and thetemperature was maintained at 1400° C. at 1 hour. Thereby, anitrogen-hydrogen treatment (refiring process) was carried out. Bypulverizing the obtained phosphor powders lightly, the respectivephosphors of Example II-9 and Example II-10 were prepared.

The luminescent characteristics of the resultant phosphor were examinedin a manner described earlier. The luminescent characteristics measuredare shown in Table II-3. From the result, it is evident that theemission intensity can be enhanced by performing a nitrogen-hydrogentreatment. This is probably because a change in the reductive conditionsof Ce, the activation element, affected the emission positively.

Examples II-11, II-12

An phosphor was prepared by the same procedure as Example II-3 exceptthat, in the secondary firing step of Example II-3, a CaSiN₂ powder thesame as that prepared in Example II-4 was added in addition to theprimary fired product and mixed, before the secondary nitriding step.

When mixing the CaSiN₂ powder with the primary fired product, the weightratio between the nitrogen-containing alloy and the CaSiN₂ powder wasadjusted so that the charge compositions ofCa_(0.75)La_(2.4)Ce_(0.1)Si₆N₁₁ (Example II-11) andCa_(1.35)La_(2.0)Ce_(0.1)Si₆N₁₁ (Example II-12), described in TableII-1, could be obtained. The phosphor powders of Example II-11 andExample II-12 were thereby prepared.

The luminescent characteristics of the resultant phosphor were examinedin a manner described earlier. The luminescent characteristics measuredare shown in Table II-3. This result indicates that a phosphor emittingyellow green light can be changed into one emitting yellow light byadding Ca on the way that it is produced using an alloy as the phosphormaterial.

The temperature characteristics I(130)/I(25) of the phosphor of ExampleII-11 was 65%.

Example II-13

A Ce_(0.1)Ca_(0.2)La_(2.8)Si₆ alloy was produced by the same procedureas Example II-1 except that, in the section of “(Production of alloy forphosphor precursor)” of Example II-1, Ca is added as a material metaland the charge composition of the metal elements was changed so thatCe:Ca:La:Si=0.1:0.2:2.8:6 (in molar ratio).

By subsequent steps of a primary firing, secondary firing, andpulverization in the same condition as Example II-1 using the obtainedalloy as the material, an oxynitride phosphor powder of which chargecomposition was Ca_(0.2)La_(2.8)Ce_(0.1)Si₆N_(10.8)O_(0.2) was produced.

The luminescent characteristics of the resultant phosphor were examinedin a manner described earlier. The luminescent characteristics measuredare shown in Table II-3. The luminescent color of the phosphor obtainedin the present Example was yellow.

Example II-14

A white light emitting device was produced by using the phosphor powderof Example II-2, of which charge composition was La_(2.9)Ce_(0.1)Si₆N₁₁,and a blue-light emitting GaN-based LED chip (460EZ, manufactured byCree, Inc.) in combination. In order to disperse and seal theabove-mentioned phosphor powder, a silicone resin sealant (SCR-1011,manufactured by Shin-Etsu Chemical Co., Ltd.) and a dispersant (QS-30,manufactured by TOKUYAMA Corp.) were used. The weight ratio of thephosphor powder of the Example II-2:sealant:dispersant was set at5.1:97.0:3.0. After heating the mixture of them at 70° C. for 1 hour, itwas hardened by an additional heating at 150° C. for 5 hours, thereby aphosphor-containing part was formed. A surface-mount white lightemitting device was then produced using it.

The emission spectrum of the obtained light emitting device is shown inFIG. 15, and its spectral characteristics are shown in Table II-4. Asshown by the color coordinate values x and y in Table II-4, it isevident that white light emission can be realized easily with just onekind of the present phosphor.

The general color rendering index of the obtained light emitting devicewas 65. By bringing the color coordinate x close to 0.45 and the colorcoordinate y to 0.41, the general color rendering index will probably befurther improved.

Reference Example II-1

The phosphor powder of Reference Example II-1 was prepared by the sameprocedure as described in “(Secondary nitriding process)” of ExampleII-4 except for the following points. Namely, no alloy was used. Inaddition, the cerium oxide powder, lanthanum nitride powder, siliconnitride powder, and CaSiN₂ powder were used as the phosphor materials bybeing weighed out in the respective amounts described in Table II-1 andmixed altogether. Moreover, the firing temperature program over 800° C.was changed in such a way that the temperature was raised to 2000° C. ata rate of 22° C./min and maintained at 2000° C. for 5 min.

In addition, the powder X-ray diffraction pattern was measured on thephosphor obtained in the present Reference Example using the CuKα line(1.54184 Å). The result is shown in FIG. 13. FIG. 13 shows thattetragonal system P4bm or its analogous structure could be produced asthe main phase even without using an alloy as the phosphor material, butsome more impurity phases then tends to be contained than in thephosphor prepared using an alloy as the phosphor material. That tendencycould be seen more, as the substitution rate x from La to Ca got lower.In the powder X-ray diffraction pattern of the phosphor of the presentReference Example (x=0.5), the ratio of the peak intensity of themaximum peak (it indicates the peak of an impurity phase) that exists inthe 2θ range of 21° to 24° to that of the 001 plane of the intendedphase was 0.118. The value was larger than that in the case where analloy was used as the phosphor material.

The luminescent characteristics of the phosphor obtained in the presentReference Example were examined in a manner described earlier. FIG. 14shows the measured emission spectrum, and Table II-3 shows theluminescent characteristics. It is evident that the emission intensitiesof the phosphors of the present invention, prepared in Examples II-2 toII-8, are significantly higher than that of the phosphor of the presentReference Example, prepared without using an alloy as the phosphormaterial.

TABLE II-1 Charge composition (composition of synthesized substance)Reference Example II-1 Ca_(0.75)La_(2.4)Ce_(0.1)Si₆N₁₁ (x = 0.5) ExampleII-1 to II-3 La_(2.9)Ce_(0.1)Si₆N₁₁ (x = 0) Example II-4 to II-10Ca_(0.75)La_(2.4)Ce_(0.1)Si₆N₁₁ (x = 0.5) Example II-11Ca_(0.75)La_(2.4)Ce_(0.1)Si₆N₁₁ (x = 0.5) Example II-12Ca_(1.35)La_(2.0)Ce_(0.1)Si₆N₁₁ (x = 0.9) Example II-13Ca_(0.2)La_(2.8)Ce_(0.1)Si₆N_(10.8)O_(0.2) (x = 0.2) *In Table II-1, xrepresents x in formula [II].

In Table II-1, x represents x in formula [II].

TABLE II-2 Charge weight (g) of each material CeO₂ LaN Si₃N₄ CaSiN₂Reference Example II-1 0.041 0.933 0.599 0.176

TABLE II-3 Prinary firing Secodary firing (secondary nitriding process)(secondary nitriding process) Firing Firing Flux Charge Pressuretemperature × Charge Pressure temperature × (kind and Example materialAtmosphere (MPa) time material Atmosphere (MPa) time amount) Reference *Refer to N₂ 0.92 2000° C. × 0.08 h — — — — — Example II-1 Table II-2Example II-1 La_(2.9)Ce_(0.1)Si₆ alloy N₂ 27 1205° C. × 0.5 h primary N₂90 2000° C. × 3 h — fired product Example II-2 La_(2.9)Ce_(0.1)Si₆ alloyN₂ 0.92 1500° C. × 58.5 h primary N₂ 0.92 1750° C. × 7 h — fired productExample II-3 La_(2.9)Ce_(0.1)Si₆ alloy N₂ 0.92 1500° C. × 58.5 h primaryN₂ 0.92 1750° C. × 39 h — fired product Example II-4 La₄CeSi₁₀ alloy +N₂ 0.92 1580° C. × 57 h + — — — — — LaN + Si₃N₄ + 2000° C. × 0.08 hCaSiN₂ Example II-5 La₄CeSi₁₀ alloy + N₂ 0.92 1580° C. × 57 h + primaryN₂ 0.92 1580° C. × 6 h — LaN + Si₃N₄ + 2000° C. × 0.08 h fired CaSiN₂product Example II-6 La₄CeSi₁₀ alloy + N₂ 0.92 1580° C. × 57 h + primaryN₂ 0.92 1580° C. × 6 h 0.9 LaN + Si₃N₄ + 2000° C. × 0.08 h fired weight% CaSiN₂ product of MgF₂ Example II-7 La₄CeSi₁₀ alloy + N₂ 0.92 1580° C.× 57 h + primary N₂ 0.92 1580° C. × 6 h 1.36 LaN + Si₃N₄ + 2000° C. ×0.08 h fired weight % CaSiN₂ product of MgF₂ Example II-8 La₄CeSi₁₀alloy + N₂ 0.92 1580° C. × 57 h + primary N₂ 0.92 1580° C. × 6 h 0.45LaN + Si₃N₄ + 2000° C. × 0.08 h fired weight % CaSiN₂ product of MgF₂Example II-9 La₄CeSi₁₀ alloy + N₂ 0.92 1580° C. × 57 h + — — — — — LaN +Si₃N₄ + 2000° C. × 0.08 h CaSiN₂ Example II-10 La₄CeSi₁₀ alloy + N₂ 0.921580° C. × 57 h + primary N₂ 0.92 1580° C. × 6 h 0.9 LaN + Si₃N₄ + 2000°C. × 0.08 h fired weight % CaSiN₂ product of MgF₂ Example II-11La_(2.9)Ce_(0.1)Si₆ alloy N₂ 0.92 1500° C. × 58.5 h primary N₂ 0.921750° C. × 39 h — fired product + CaSiN₂ Example II-12La_(2.9)Ce_(0.1)Si₆ alloy N₂ 0.92 1500° C. × 58.5 h primary N₂ 0.921750° C. × 39 h — fired product + CaSiN₂ Example II-13Ce_(0.1)Ca_(0.2)La_(2.8)Si₆ N₂ 27 1205° C. × 0.5 h primary N₂ 90 2000°C. × 3 h — alloy fired product N2—H2 treatment condition (refiringprocess) Emission characteristics when excited by 460 nm Firing EmissionEmission peak Full width at CIE Color Charge Pressure temperature ×intensity wavelength half maximum coordinate Example material (MPa) time(a.u.) (nm) (nm) x y Reference — — — 0.451 571 142 0.461 0.512 ExampleII-1 Example II-1 — — — 0.235 533 125 0.401 0.543 Example II-2 — — —0.593 533 118 0.407 0.553 Example II-3 — — — 0.630 536 122 0.415 0.548Example II-4 — — — 0.662 574 140 0.465 0.514 Example II-5 — — — 0.731568 137 0.462 0.516 Example II-6 — — — 0.764 564 137 0.457 0.520 ExampleII-7 — — — 0.760 561 135 0.454 0.523 Example II-8 — — — 0.728 564 1380.458 0.519 Example II-9 primary Normal 1400° C. × 1 h 0.796 561 1350.461 0.519 fired pressure product Example II-10 secondary Normal 1400°C. × 1 h 0.802 556 134 0.453 0.524 fired pressure product Example II-11— — — 0.541 558 133 0.443 0.529 Example II-12 — — — 0.468 573 145 0.4660.505 Example II-13 — — — 0.420 540 127 0.425 0.538

TABLE II-4 Charge composition Emission characteristics (composition ofColor Color Example synthesized substance) coordinate x coordinate yExample II-14 La_(2.9)Ce_(0.1)Si₆N₁₁ 0.300 0.327

INDUSTRIAL APPLICABILITY

The present invention can be used in any field of industry. For example,it can be preferably used in the fields where light is used such asilluminating devices and displays. Among them, it is suitable forhigh-power LED lamps for general lighting, and more particularly forwarm white LEDs with high brightness, high color rendering, andrelatively low color temperature.

The present invention has been explained in detail above with referenceto specific embodiments. However, it is evident to those skilled in theart that various modifications can be added thereto without departingfrom the intention and the scope of the present invention.

The present application is based on Japanese Patent Application (PatentApplication No. 2007-109270) filed on Apr. 18, 2007 and their entiretiesare incorporated herewith by reference.

1. A phosphor comprising a crystal phase represented by formula [I],R_(3−x−y−z+w2)M_(z)A_(1.5x+y−w2)Si_(6−w1−w2)Al_(W1+w2)O_(y+w1)N_(11−y−w1)  [I]wherein, R represents at least one kind of a rare-earth element selectedfrom the group consisting of La, Gd, Lu, Y and Sc, wherein La is used inan amount of at least 70 mol percent relative to the total amount of R,M represents at least one kind of a metal element selected from thegroup consisting of Ce, Eu, Mn, Yb, Pr and Tb, A represents at least onekind of a bivalent metal element selected from the group consisting ofBa, Sr, Ca, Mg and Zn, and x, y, z, w1 and w2 are the numeric valueswherein:( 1/7)≦(3−x−y−z+w2)/6<(½),0<(1.5x+y−w2)/6<(9/2),0<x<3,0≦y<2,0<z<1,0<w1≦5,0≦w2≦5, and0≦w1+w2≦0.4, wherein color coordinates x and y, in CIE standardcolorimetric system, of the luminescent color when excited with lighthaving 460-nm wavelength are in the ranges of 0.420≦x≦0.600 and0.400≦y≦0.570, respectively.
 2. The phosphor according to claim 1,wherein a wavelength of emission peak when excited with light of 460-nmwavelength is 480 nm or longer.
 3. A phosphor comprising a crystal phaserepresented by formula [II], obtained by, as at least a part of a rawmaterial, an alloy comprising two or more kinds of the metal elementsthat are in said crystal phase, whereinR_(3−x−y−z+w2)M_(z)A_(1.5x+y−w2)Si_(6−w1−w2)Al_(W1+w2)O_(y+w1)N_(11−y−w1)  [II]wherein, R represents at least one kind of a rare-earth element selectedfrom the group consisting of La, Gd, Lu, Y and Sc, wherein La is used inan amount of at least 70 mol percent relative to the total amount of R,M represents at least one kind of a metal element selected from thegroup consisting of Ce, Eu, Mn, Yb, Pr and Tb, A represents at least onekind of a bivalent metal element selected from the group consisting ofBa, Sr, Ca, Mg and Zn, and x, y, z, w1 and w2 are the numeric valueswherein:( 1/7)≦(3−x−y−z+w2)/6<(½),0≦(1.5x+y−w2)/6<(9/2),0≦x<3,0≦y<2,0<z<1,0≦w2≦5, and0≦w1+w2≦0.4, wherein the color coordinates x and y, in CIE standardcolorimetric system, of the luminescent color when excited with lighthaving 460-nm wavelength are in the ranges of0.320≦x≦0.600 and0.400≦y≦0.570.
 4. The phosphor according to claim 3, wherein awavelength of emission peak when excited with light of 460-nm wavelengthis 480 nm or longer.
 5. The phosphor according to claim 4, wherein anemission spectrum when excited with light of 460-nm wavelength satisfiesthe formula [B],I(B)/I(A)≦0.88  [B] wherein, I(A) represents an emission intensity ofthe maximum peak wavelength that is present in the wavelength range of500 nm or longer and 550 nm or shorter, and I(B) represents an emissionintensity of the wavelength that is longer than the maximum peakwavelength by 45 nm.
 6. The phosphor according to claim 3, wherein inthe powder X-ray diffraction pattern measured with CuKα line (1.54184Å), a peak exists at 2θ from 17° to 20°, and a peak intensity ratio I,related to a peak present at 2θ from 21° to 24°, is 0.05 or smaller,where the peak intensity ratio I is defined by, in the powder X-raydiffraction pattern at 2θ ranging from 10° to 60°, the ratio of theheight Ip of the peak present at 2θ from 21° to 24°, to the height Imaxof the most-intensive peak present at 2θ from 17° to 20°, and the valuesof the peak intensities are obtained after background correction.
 7. Thephosphor according to claim 3, wherein, in the formula [II], x and ysatisfy0<(1.5x+y−w2)/6<(9/2) and0<x<3.
 8. The phosphor according to claim 3, wherein, the full width athalf maximum of the emission peak when excited with light of 460-nmwavelength is 100 nm or longer.
 9. A method for producing a phosphorcomprising a crystal phase represented by the formula [II], obtained by,as at least a part of a raw material, an alloy comprising two or morekinds of the metal elements that are included in said crystal phase,comprising nitriding the alloy by firing in a nitrogen-containingatmosphere, whereinR_(3−x−y−z+w2)M_(z)A_(1.5x+y−w2)Si_(6−w1−w2)Al_(W1+w2)O_(y+w1)N_(11−y−w1)  [II]wherein, R represents at least one kind of a rare-earth element selectedfrom the group consisting of La, Gd, Lu, Y and Sc, wherein La is used inan amount of at least 70 mol percent relative to the total amount of R,M represents at least one kind of a metal element selected from thegroup consisting of Ce, Eu, Mn, Yb, Pr and Tb, A represents at least onekind of a bivalent metal element selected from the group consisting ofBa, Sr, Ca, Mg and Zn, and x, y, z, w1 and w2 are the numeric values:( 1/7)≦(3−x−y−z+w2)/6<(½),0≦(1.5x+y−w2)/6<(9/2),0≦x<3,0≦y<2,0<z<1,0≦w1≦50≦w2≦5, and0≦w1+w2≦0.4, wherein the color coordinates x and y, in CIE standardcolorimetric system, of the luminescent color when excited with lighthaving 460-nm wavelength are in the ranges of0.320≦x≦0.600 and0.400≦y≦0.570.
 10. The method for producing a phosphor, according toclaim 9, wherein the raw material comprises the alloy and a nitride. 11.A phosphor-containing composition comprising: said phosphor according toclaim 1 and a liquid medium.
 12. A light emitting device comprising: afirst luminous body and a second luminous body that emits visible lightwhen irradiated with light from said first luminous body, wherein saidlight emitting device comprises, as said second luminous body, a firstphosphor comprising at least one kind of said phosphor according toclaim
 1. 13. A light emitting device according to claim 12, wherein saidlight emitting device comprises, as said second luminous body, a secondphosphor comprising at least one kind of a phosphor of which wavelengthof emission peak is different from that of said first phosphor.
 14. Anilluminating device comprising a light emitting device according toclaim
 12. 15. A display comprising a light emitting device according toclaim
 12. 16. A nitrogen-containing compound comprising a crystal phaserepresented by the formula [I],R_(3−x−y−z+w2)M_(z)A_(1.5x+y−w2)Si_(6−w1−w2)Al_(W1+w2)O_(y+w1)N_(11−y−w1)  [I]where R represents at least one kind of a rare-earth element selectedfrom the group consisting of La, Gd, Lu, Y and Sc, wherein La is used inan amount of at least 70 mol percent relative to the total amount of R,M represents at least one kind of a metal element selected from thegroup consisting of Ce, Eu, Mn, Yb, Pr and Tb, A represents at least onekind of a bivalent metal element selected from the group consisting ofBa, Sr, Ca, Mg and Zn, x, y, z, w1 and w2 are the numeric values in thefollowing ranges:( 1/7)≦(3−x−y−z+w2)/6<(½)0<(1.5x+y−w2)/6<(9/2),0<x<3,0≦y<2,0<z<1,0≦w1≦5,0≦w2≦5, and0≦w1+w2≦0.4, wherein the color coordinates x and y, in CIE standardcolorimetric system, of the luminescent color when excited with lighthaving 460-nm wavelength are in the ranges of0.320≦x≦0.600 and0.400≦y≦0.570.
 17. The phosphor according to claim 1, wherein w1+w2=0.18. The phosphor according to claim 3, wherein w1+w2=0.
 19. The methodfor producing a phosphor according to claim 9, wherein w1+w2=0.
 20. Thenitrogen containing compound according to claim 16, wherein w1+w2=0.